Latent Print Examination and Human Factors: 

Improving the Practice through a Systems Approach 

The Report of the Expert Working Group on Human Factors in Latent Print Analysis 

February 2012 

National Institute of 

Standards and Technology 
Latent Print Examination and 

Human Factors: Improving the 

Practice through a Systems 

Approach 

The Report of the Expert Working Group on 

Human Factors in Latent Print Analysis

In Memoriam

This report is dedicated to the memory of Danny Greathouse, a valued 

contributor to this study and a friend who will be missed.
Latent Print Examination and Human Factors: Improving the 

Practice through a Systems Approach was produced with funding from 

the U.S. Department of Justice’s National Institute of Justice and in 

collaboration with the Law Enforcement Standards Office in the U.S. 

Department of Commerce’s National Institute of Standards and 

Technology. 

Opinions or points of view expressed in this report are those of the authors

and do not necessarily reflect the official position or policies of the U.S. 

Department of Justice or the U.S. Department of Commerce. Mention of 

commercial products or services in this report does not imply approval or 

endorsement by the National Institute of Standards and Technology, nor 

does it imply that such products or services are necessarily the best 

available for the purpose.

Suggested citation format: Expert Working Group on Human Factors in 

Latent Print Analysis. Latent Print Examination and Human Factors: 

Improving the Practice through a Systems Approach. U.S. Department of 

Commerce, National Institute of Standards and Technology. 2012.
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

iii

Table of Contents

Introduction...................................................................................................vi 

Chapter 1: The Latent Print Examination Process and Terminology.............................1 

Chapter 2: Human Factors and Errors................................................................21 

Chapter 3: Interpreting Latent Prints..................................................................39 

Chapter 4: Looking Ahead to Emerging and Improving Technology............................77 

Chapter 5: Reports and Documentation...............................................................90 

Chapter 6: Testimony....................................................................................113 

Chapter 7: A Systems Approach to the Work Environment.....................................140 

Chapter 8: Training and Education...................................................................163 

Chapter 9: Human Factors Issues for Management...............................................172 

Chapter 10: Summary of Recommendations........................................................197 

Bibliography................................................................................................211 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

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List of Boxes, Figures, and Tables

Boxes 

Box 1.1: Terminology 

Box 1.2: Misconceptions about “Bias” in Science 

Box 1.3: Probabilities, Likelihood Ratios, and Individualization

Box 2.1: Daubert v. Merrell Dow Pharmaceuticals, Inc., and “Error Rates”

Box 2.2: How Prevalence, Sensitivity, and Specificity Affect the Posterior Probability of a 

Correct Positive Identification

Box 2.3: The Zero Numerator Problem 

Box 2.4: Selected Results of the Noblis-FBI Experiment 

Box 3.1: Studies on the Effect of Biasing Information 

Box 7.1: Three Mile Island Accident

Box 9.1: Learning from Others: Benchmarking in Forensic Science 

Box 9.2: High-Reliability Organizations

Box 9.3: Accreditation in the European Union 

Box 9.4: Certification and Testing for the Practice of Medicine 

Figures

Figure 1.1: The Latent Print Examination Process Map

Figure 1.2: Analysis phase of ACE-V 

Figure 1.3: Comparison phase of ACE-V 

Figure 1.4: A latent print and exemplar prints 

Figure 1.5: Evaluation phase of ACE-V 

Figure 1.6: Verification phase of ACE-V 

Figure 3.1: Level 1 Detail features

Figure 3.2: Examples of skin distortion on prints of the same finger with arrows indicating 

location of the same minutiae in different impressions 

Figure 4.1: Example of a color replacement filter to remove color from a playing card

Figure 4.2: Example of filters used to adjust color levels and to reverse the colors 

Figure 4.3: An example of some minutiae locations in a fingerprint

Figure 7.1: A human factors framework 

Figure 7.2: The Hamilton Veale contrast sensitivity test

Figure 7.3: An example of a poorly designed workstation 

Figure 7.4: An example of a poorly designed user interface 

Figure 9.1: Latent print from an ashtray and an exemplar print 

Figure 9.2: Components of a productive system adapted to a latent print unit 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

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Tables

Table 1.1: Illustrations of some friction ridge minutiae

Table 1.2: Posterior odds of identity for evidence with a likelihood ratio of 1,000,000 in 

populations in which everyone has the same prior odds on being the source of a latent 

print 

Table 2.1: Types of errors and correct conclusions in a binary classification task 

Table 2.2: Outcomes of a hypothetical experiment that estimates an examiner’s sensitivity and 

specificity

Table 2.3: Hypothetical data to show probability of identifications in an 80-20 mix 

Table 2.4: Hypothetical data to show probability of identifications in a 10-90 mix

Table 2.5: Types of errors and correct conclusions in a binary classification task with the option 

of not deciding 

Table 2.6: Concordancy in judgments of two examiners 

Table 2.7: Concordancy with desired outcomes as determined by experts 

Table 2.8: Outcomes for pairs judged to be “of value for individualization” 

Table 2.9: Accuracy and error rates for exclusions and identifications in pairs judged to be “of 

value for individualization” and leading to exclusions or identifications 

Table 3.1: Distribution for the general patterns on fingerprints from the left and right hands of 

males (89,755,960 fingers) 

Table 3.2: Distribution for the general patterns on fingerprints from the right thumb and little 

fingers of males (17,951,192 fingers) 

Table 3.3: Examples of statistics on subclassifications

Table 3.4: Relative frequencies for different types of minutiae according to Gupta (1968), 

Osterburg et al. (1977), and Lin et al. (1982) 

Table 3.5: Relative frequencies for different types of minutiae according to Santamaria Beltran 

(1953), Kingston (1964), Sclove (1979-1980), and Stoney (1985) 

Table 6.1: Strength of likelihood ratios in support of evidence 

Table 7.1: Recommended eye examinations frequency for adult patients 

Table 7.2: Definitions of usability goals and questions that apply specifically to latent print 

examiners

Table 7.3: Characteristics to consider when designing latent print examiners’ work environments 

Table 7.4: Characteristics regarding each element of an environment to be considered 

Table 9.1: Possible outcomes of the comparison of the latent and exemplar prints in Figure 9.1 

Table 9.2: Concordance table listing possible “errors” for conclusions in Table 9.1
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

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Introduction

Fingerprints have provided a valuable method of personal identification in forensic science and 

criminal investigations for more than 100 years.1 Fingerprints left at crime scenes generally are 

latent prints—unintentional reproductions of the arrangement of ridges on the skin made by the 

transfer of materials (such as amino acids, proteins, polypeptides, and salts) to a surface. Palms 

and the soles of feet also have friction ridge skin that can leave latent prints. The examination of 

a latent print consists of a series of steps involving a comparison of the latent print to a known 

(or exemplar) print. Courts have accepted latent print evidence for the past century.2 However, 

several high-profile cases in the United States and abroad have highlighted the fact that human 

errors can occur,3 and litigation and expressions of concern over the evidentiary reliability of 

latent print examinations and other forensic identification procedures has increased in the last 

decade.4

 

“Human factors” issues can arise in any experience- and judgment-based analytical process such 

as latent print examination. Inadequate training, extraneous knowledge about the suspects in the 

case or other matters, poor judgment, health problems, limitations of vision, complex 

technology, and stress are but a few factors that can contribute to errors. A lack of standards or 

quality control, poor management, insufficient resources, and substandard working conditions 

constitute other potentially contributing factors. 

In addition to reaching correct conclusions in the matching process, latent print examiners are 

expected to produce records of the examination and, in some cases, to present their conclusions 

and the reasoning behind them in the courtroom. Human factors issues related to the 

documentation and communication of an examiner’s work and findings therefore merit attention

as well. 

The study of human factors focuses on the interaction between humans and products, decisions, 

procedures, workspaces, and the overall environment encountered at work and in daily living.5

Human factors analysis can advance our understanding of the nature of errors in complex work 

settings. Most preventable, adverse events are not just the result of isolated or idiosyncratic 

behavior but are in part caused by systemic factors.

6

 

1 Barnes, J. “History.” In The Fingerprint Sourcebook. National Institute of Justice, 2011. Cole, S. Suspect 

Identities: A History of Fingerprinting and Criminal Identification. Harvard University Press, 2001. 

The forensic science community can benefit 

from the application of human factors research to enhance quality and productivity in friction 

2 Mnookin, J. “Fingerprint Evidence in an Age of DNA Profiling.” Brooklyn Law Review, 67 (2001): 13.

3 E.g., R. v. Smith, 2011 EWCA Crim. 1296; Bertino, A. and P. Bertino. Forensic Science: Fundamentals and 

Investigations. South-Western Educational Publishing, 2009 (Stephen Cowans case); U.S. Department of Justice, 

Office of the Inspector General. A Review of the FBI’s Handling of the Brandon Mayfield Case (Unclassified and 

Redacted). U.S. Department of Justice, March 2006; and Sweeney, C. “Lord Advocate to Appear Before Shirley 

McKie Fingerprint Inquiry.” The Times, October 21, 2008. 4 E.g., Leveson, B. Expert Evidence in Criminal Courts—The Problem, Address to the Forensic Science Society, 

Kings College, University of London, November 18, 2010. For discussion of specific cases, see Chapter 6.

5 Sanders, M. and E. McCormick. Human Factors in Engineering and Design, 7th ed. McGraw-Hill Companies, 

1993.

6 National Academy of Sciences, Institute of Medicine, Committee on Quality of Health Care in America. To Err Is 

Human: Building A Safer Health System. National Academies Press, 1999.
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

vii 

ridge examinations and to reduce the likelihood and consequences of human error at various 

stages in the interpretation of evidence. 

To further this effort, the National Institute of Justice (NIJ) Office of Investigative and Forensic 

Sciences (OFIS) within the U.S. Department of Justice and the National Institute of Standards 

and Technology’s (NIST’s) Law Enforcement Standards Office (OLES) sponsored the work of 

this expert panel to examine human factors in latent print analysis and to develop 

recommendations to reduce the risk of error and improve the practice of latent print analysis.

1. The Expert Working Group on Human Factors in Latent Print Analysis

The Expert Working Group on Human Factors in Latent Print Analysis was convened in 

December 2008 and charged with conducting a scientific assessment of the effects of human 

factors on forensic latent print analysis. A scientific assessment, as defined by the Office of 

Management and Budget, “is an evaluation of a body of scientific or technical knowledge which

typically synthesizes multiple factual inputs, data, models, and assumptions, and/or applies best 

professional judgment to bridge uncertainties in the available information.”7

 

The Working Group was charged with: 

• Developing an understanding of the role of human factors and their contributions to 

errors in latent print analysis through an evidence-based review of literature, case studies, 

and previous analyses; 

• Evaluating approaches to reducing errors in terms of their efficacy, appropriateness in 

different settings and circumstances, cost, scientific basis, feasibility, institutional barriers 

to implementation, associated risks, and the quality of evidence supporting the approach; 

• Providing guidance to the latent print analysis community on the practical, scientific, and 

policy outcomes of its work through peer-reviewed publications, presentations at 

conferences and meetings, and government-sponsored publications; 

• Providing guidance to policy-makers and government agencies in promoting a national 

agenda for error reduction in latent print analysis; 

• Attempting to develop credible estimates of the incidence, severity, and costs of 

errors; and

• Making recommendations for future research. 

Working Group members were selected because of their expertise in the forensic sciences or 

another relevant field and the ability to balance scientific rigor with practical and regulatory 

constraints. The Working Group consisted of experts from forensic disciplines, statisticians, 

psychologists, engineers, other scientific experts, legal scholars, and representatives of 

professional organizations. 

The Working Group met 9 times over the course of 2 1/2 years and heard presentations from 

experts in human factors, vision science, laboratory design, latent print identification, and 

interpretation in forensic science. Each chapter in this report was developed by a subgroup of the 

 

7 Office of Management and Budget. Final Information Quality Bulletin for Peer Review. Office of Management 

and Budget, December 15, 2004.
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

viii

Working Group, reviewed by the entire Working Group, edited by a committee within the group, 

and reviewed again by a set of independent experts. The report was developed through a 

consensus process in which each Working Group member had an opportunity to influence the 

recommendations and writing. Despite the diversity of backgrounds and views, the Working 

Group was able to reach substantial agreement on many important issues, not limited to the 

formal recommendations. On some matters, however, an irreducible range of opinions remained, 

and particular chapters indicate those issues. 

2. About the Sponsors

NIJ is the research, development, and evaluation agency of the U.S. Department of Justice and is 

dedicated to researching crime control and justice issues. NIJ provides objective, independent, 

evidence-based knowledge and tools to meet the challenges of crime and justice. The Office of 

Investigative and Forensic Sciences (OIFS) is the federal government’s lead agency for forensic 

science research and development as well as for the administration of programs that provide 

direct support to crime laboratories and law enforcement agencies to increase their capacity to 

process high-volume cases, to provide needed training in new technologies, and to provide 

support to reduce backlogs. Forensic science program areas include Research and Development 

in Basic and Applied Forensic Sciences, Coverdell Forensic Science Improvement Grants, DNA 

Backlog Reduction, Solving Cold Cases with DNA, Postconviction DNA Testing Assistance, 

National Missing and Unidentified Persons System (NamUs), and Forensic Science Training 

Development and Delivery. 

NIST’s mission is to advance measurement science, standards, and technology. It accomplishes 

these actions for the forensic science community through the OLES Forensic Science Program. 

The OLES Forensic Science Program directs research efforts to develop performance standards, 

measurement tools, operating procedures, guidelines, and reports that will advance the field of 

forensic science. OLES also serves the broader public safety community through the 

promulgation of standards in the areas of protective systems; detection, enforcement, and 

inspection technologies; public safety communication; and counterterrorism and response 

technologies. 

3. Organization of This Report 

Chapter 1 provides an overview of the Analysis, Comparison, Evaluation, and Verification 

(ACE-V) process for the examination of latent prints. The chapter also explains certain 

terminology used throughout the report. 

Chapter 2 outlines the general ideas behind human factors and organizational theory. It also 

addresses the nature of errors in latent print analysis, the reasons for identifying them or 

measuring their prevalence, and possible ways to estimate accuracy and error rates.

Chapter 3 describes, defines, and clarifies the interpretative stages of latent print comparisons. In 

addition, it describes the current state of knowledge, based upon published research, and 

discusses what this research suggests about potential concerns and pitfalls in the interpretive 

process. 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

ix

Chapter 4 surveys new and forthcoming methods, technologies, and techniques. It examines 

research needs and ways to improve existing technologies for recording and storing exemplars, 

for utilizing automated searches to locate exemplars for further comparison, and for conducting 

latent print examinations.

Chapter 5 addresses written reports that summarize and document the results of friction skin 

impression examinations. Best practices in report writing and documentation increase the 

likelihood that the evidence is scientifically accurate and will be used appropriately in the 

administration of criminal justice. The chapter describes the purposes and value of reporting and 

documenting examinations and makes suggestions regarding the content of these materials. 

Appendices provide examples of sample reports. 

Chapter 6 discusses trial and pretrial communications from the expert to lawyers, judges, and 

juries. It reviews the more important legal rules and principles that apply to these activities and 

surveys the types of testimony that might be provided at trial. 

Chapter 7 focuses on the conditions under which latent print work is performed that can affect 

quality in the latent print examination process. It considers issues such as scheduling, lighting, 

workstations, interruptions, and workplace design. 

Chapter 8 reviews the current status of education and training for latent print examiners, 

requirements and evaluation criteria, and curricula. It makes recommendations for training and 

educational programs to improve quality and accuracy in latent print analysis and reporting. 

Chapter 9 focuses on the role of management in developing and maintaining the system for 

producing high-quality results. It reviews the components of a quality organization focused on 

latent print analysis. These include management, personnel, accreditation, certification, 

proficiency testing, and a systems approach to error identification and mitigation. It recommends 

actions that managers and the latent print community should take to create or maintain quality 

latent print units.

Chapter 10 summarizes the most important parts of the preceding chapters. It draws the 

recommendations from Chapters 3 through 9 into categories that may be helpful for latent print 

examiners, managers, research funding agencies, researchers, policymakers, and jurists. An 

appendix lists all formal recommendations in order of their appearance in this report. 

Although this report explicitly addresses only the procedures for performing a latent fingerprint 

examination and communicating the results, much of the analysis and many of the 

recommendations are applicable to other forensic science disciplines. Issues of cognitive bias, 

standardization of procedures, documentation of examinations, working conditions, error 

detection and correction, and accuracy in testimony—among many others—cut across the 

forensic sciences. By identifying and managing the human factors issues relevant to latent print 

analysis, the latent print community not only can enhance the quality and accuracy of its 

contributions to the justice system but also can set an example for other forensic disciplines. The 

Working Group hopes that this report will assist in this effort. 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

x 

4. Contributors to This Report

The Expert Working Group on Human Factors in Latent Print Analysis 

The Working Group relied upon the contributions of many individuals. The opinions presented 

over the course of the Working Group’s deliberation reflect personal experiences and research. 

The views in this report do not express the official positions of the institutions with which the 

members are affiliated. 

David H. Kaye, JD, MS, (Editor in Chief) Distinguished Professor and Weiss Family Scholar, 

Dickinson School of Law and Graduate Faculty Member, Forensic Science Program, Eberly 

College of Science, Pennsylvania State University

Thomas Busey, PhD, (Editorial Committee) Professor, Department of Psychological and Brain 

Sciences, Indiana University

Melissa R. Gische, MFS, (Editorial Committee) Physical Scientist/Forensic Examiner, Latent 

Print Operations Unit, Federal Bureau of Investigation Laboratory 

Gerry LaPorte, (Editorial Committee) Forensic Policy Program Manager, National Institute of 

Justice

Colin Aitken, PhD, Professor of Forensic Statistics, School of Mathematics, University of 

Edinburgh 

Susan Ballou, MS, Law Enforcement Standards Office, National Institute of Standards and

Technology

Leonard Butt, Chair, Scientific Working Group on Friction Ridge Analysis, Study and 

Technology 

Christophe Champod, PhD, Professor, Institut de Police Scientifique, École des Sciences 

Criminelles, Université de Lausanne

David Charlton, PhD, Surrey and Sussex Police Forensic Services, UK 

Itiel E. Dror, PhD, University College London and Cognitive Consultants International 

Jules Epstein, JD, Associate Professor of Law, Widener University School of Law 

Robert J. Garrett, Past President and Chairman of the Board, International Association for 

Identification

Max M. Houck, PhD, Co-Chair and Principal Analyst, Anser 

Edward J. Imwinkelried, JD, Edward L. Barrett, Jr. Professor of Law, Director of Trial 

Advocacy, University of California, Davis 

Ralph Keaton, Executive Director, American Society of Crime Laboratory Directors/Laboratory 

Accreditation Board

Glenn Langenburg, MS, Forensic Scientist, Minnesota Bureau of Criminal Apprehension 

Deborah A. Leben, MS, Lead Fingerprint Specialist, United States Secret Service, Department 

of Homeland Security

Alice Maceo, Forensic Lab Manager, Las Vegas Metropolitan Police Department Forensic 

Laboratory

Kenneth F. Martin, Detective Lieutenant (Retired), Crime Scene Services Section, 

Massachusetts State Police

Jennifer L. Mnookin, JD, PhD, Professor of Law, University of California, Los Angeles 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

xi

Cedric Neumann, PhD, Assistant Professor, Department of Statistics and Forensic Science

Program, Eberly College of Science, Pennsylvania State University

Joe Polski, Forensics Committee Member, International Association of Chiefs of Police 

Maria Antonia Roberts, MS, Research Program Manager, Latent Print Support Unit, Federal 

Bureau of Investigation Laboratory 

Scott A. Shappell, PhD, Professor, Department of Industrial Engineering, Clemson University 

Lyle Shaver, Forensic Scientist Supervisor, Virginia Department of Forensic Science

Sargur N. Srihari, PhD, SUNY Distinguished Professor, Department of Computer Science and 

Engineering, State University of New York at Buffalo

Hal S. Stern, PhD, Professor, Department of Statistics, University of California, Irvine 

David Stoney, PhD, Chief Scientist, Stoney Forensic, Inc. 

Anjali Swienton, MFS, JD, Director of Outreach, National Clearinghouse for Science, 

Technology and the Law (NCSTL), Stetson University College of Law

Mary Theofanos, MS, Computer Scientist, Information Access Division, Information Technology 

Laboratory, National Institute of Standards and Technology 

Robert M. Thompson, Program Manager, Forensic Data Systems, Law Enforcement Standards 

Office, National Institute of Standards and Technology 

John Vanderkolk, Laboratory Manager, Indiana State Police Laboratory

Maria Weir, MA, Supervising Forensic Identification Specialist, Los Angeles County Sheriff’s 

Department

Kasey Wertheim, MBA, Co-Chair, President, and CEO, Complete Consultants Worldwide, 

LLC 

Staff 

Melissa Taylor, Study Director, Law Enforcement Standards Office, National Institute of 

Standards and Technology

Mark D. Stolorow, Director, Law Enforcement Standards Office, National Institute of Standards 

and Technology

Jennifer L. Smither, Lead Editor, Science Applications International Corporation 

Kathi E. Hanna, PhD, Consultant Writer and Editor 

Shannan Williams, MPP, Program Assistant, Booz Allen Hamilton

Acknowledgements

The Working Group gratefully acknowledges the following individuals for their contributions to 

the development of this document. 

Bruce Budowle, PhD, Executive Director, Institute of Applied Genetics, Professor, Department 

of Forensic and Investigative Genetics, University of North Texas Health Science Center

Mike Campbell, Training Coordinator, Ron Smith and Associates, Inc. 

Yee-Yin Choong, PhD, Industrial Engineer, Information Technology Laboratory, National 

Institute of Standards and Technology 

Sarah Chu, Innocence Project
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

xii

Gislin Dagnelie, PhD, Associate Professor of Ophthalmology, Johns Hopkins University School 

of Medicine 

Susanne M. Furman, PhD, Cognitive Scientist, Information Technology Laboratory, National 

Institute of Standards and Technology 

Danny Greathouse, Former Special Agent, Federal Bureau of Investigation

Marc Green, PhD, Visual Expert Human Factors, Marc Green, Phd and Associates

Austin Hicklin, Noblis

James Johnson, Forensic Consultant, Contracted to United States Secret Service

Philip J. Kellman, PhD, Professor, Department of Psychology, University of California, Los 

Angeles

Jonathan J. Koehler, PhD, Beatrice Kuhn Professor of Law, Northwestern University School of Law 

Kevin Lothridge, Chief Executive Officer, National Forensic Science Technology Center

Tamas Makany, PhD, Cognitive Psychologist 

Stephen B. Meagher, Federal Bureau of Investigation Laboratory (Retired)

Ross J. Michaels, PhD, Supervisory Computer Scientist, National Institute of Standards and 

Technology 

Ken Mohr, Senior Forensic Programmer/Planner, Crime Lab Design 

Keith Morris, PhD, Associate Professor/Director, Ming Hsieh Distinguished Professor, Forensic 

and Investigative Science, West Virginia University

Kamran Nouri, Senior Consultant, ABS Consulting 

Ron Smith, President, Ron Smith and Associates, Inc.

Brian Stanton, MS, Cognitive Scientist, Information Technology Laboratory, National Institute 

of Standards and Technology 

Lois Tully, Former Deputy Director, Office of Investigative and Forensic Sciences, National 

Institute of Justice

Lee N. Vanden Heuvel, Manager, Incident Investigation and Root Cause Analysis Services, 

ABS Consulting

Douglas A. Wiegmann, University of Wisconsin-Madison 

David D. Woods, PhD, Professor, The Ohio State University

Reviewers

Individuals chosen for their diverse perspectives and technical expertise reviewed this report in 

draft form and provided constructive suggestions. These reviewers were not asked to approve or 

endorse any conclusions or recommendations in the draft report, nor did they review this final 

version before its release. Responsibility for the final content of this report rests with the 

members of the Working Group. 

John P. Black, Senior Consultant, Ron Smith and Associates, Inc. 

Deborah A. Boehm-Davis, George Mason University

David L. Grieve, Illinois State Police (Retired)

Austin Hicklin, Noblis 

Kevin Lothridge, Chief Executive Officer, National Forensic Science Technology Center
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Introduction 

xiii

Jennifer S. Mihalovich, F-ABC, Criminalist III, Oakland Police Department Criminalistics 

Division

Roger C. Park, James Edgar Hervey Distinguished Professor of Law, U.C. Hastings College of 

Law, San Francisco

Peter Peterson, PhD, Physical Scientist/Forensic Examiner, Federal Bureau of Investigation

Laura Tierney, Certified Latent Print Examiner

Mark L. Weiss, PhD, Division Director, Behavioral and Cognitive Sciences, National Science 

Foundation 

Sandy Zabell, Professor of Mathematics and Statistics, Northwestern University
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 1: The Latent Print Examination Process and Terminology 

1 

Chapter 1: The Latent Print Examination Process and Terminology

Introduction

The conventional procedure for associating impressions of friction ridge skin by a latent print 

examiner involves four phases known as Analysis, Comparison, Evaluation, and Verification 

(ACE-V). This chapter describes the ACE-V process, notes some of its limitations, identifies 

areas where human factors should be considered, and defines certain terms used throughout this 

report.

Box 1.1: Terminology

ACE-V: An acronym for Analysis, Comparison, Evaluation, and Verification. The ACE-V process is 

described in section 1.1. 

Bias and error: Defined and discussed in section 1.2. 

Exemplar or known prints: Prints deliberately collected from an individual, usually fingerprints. Exemplar 

prints can be collected electronically or by using ink on paper cards. Exemplars may be called ten-prints

when impressions of all ten fingers are taken. Exemplar prints collected during criminal arrests normally 

include one rolled (from one side of the nail to the other) print of each finger pad and a plain or slap 

impression of each finger.

Focal point: A small region containing distinguishing features within a print.

Forensic service provider: A laboratory or unit that examines physical evidence in criminal matters and 

provides testimony and reports about the examination findings. In this report, the term is used 

interchangeably with agency. 

Latent print: Unintentional reproduction of the arrangement of ridges on the skin on the underside of the 

hands or feet made by the transfer of materials from the skin to a surface. This report uses the term print

or latent print to denote impressions from all regions of friction ridge skin unless a more specific term 

such as “fingerprint” or “palm print” is used. 

Latent print examination: The study of latent and exemplar prints to help determine the source of the 

latent print. Because prints come from the friction ridge area of the skin on the hands or feet, latent print 

analysis is sometimes referred to as friction ridge analysis. As discussed below, “Analysis” and 

“Comparison” also have specialized meanings in “ACE-V;” therefore, this report generally uses the term 

“examination” rather than “analysis” or “comparison” when referring to the totality of work of latent print 

examiners.

Latent print examiner: The individual who conducts the latent print examination, also called latent print 

analyst.
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 1: The Latent Print Examination Process and Terminology 

2 

Minutiae: Events along a ridge path, including bifurcations (points at which one friction ridge divides into 

two friction ridges), dots (isolated friction ridge units that have lengths similar their widths), and ridge 

endings (the abrupt end of ridges), as illustrated in Table 1.1. 

Bifurcation Dot Ridge Ending

 

Table 1.1: Illustrations of some friction ridge minutiae8

1.1 The ACE-V Process

In broad strokes, a latent print examination using the ACE-V process proceeds as follows: 

Analysis refers to an initial information-gathering phase in which the examiner studies the 

unknown print to assess the quality and quantity of discriminating detail present. The examiner 

considers information such as substrate, development method, various levels of ridge detail, and 

pressure distortions. A separate analysis then occurs with the exemplar print. Comparison is the 

side-by-side observation of the friction ridge detail in the two prints to determine the agreement 

or disagreement in the details. In the Evaluation phase, the examiner assesses the agreement or 

disagreement of the information observed during Analysis and Comparison and forms a 

conclusion. Verification in some agencies is a review of an examiner’s conclusions with 

knowledge of those conclusions; in other agencies, it is an independent re-examination by a 

second examiner who does not know the outcome of the first examination. 

Figure 1.1, developed by members of the Working Group, describes the steps of the ACE-V 

process as currently practiced by the latent print examination community. The Latent Print 

Examination Process Map’s purpose is to facilitate discussion about key decision points in the 

ACE-V process. This chapter briefly describes each step in ACE-V, although the sequence of 

some of the steps may vary in practice.

 

8 Images adapted from Champod, C. Reconnaissance Automatique et Analyse Statistique des Minuties sur les 

Empreintes Digitales. PhD Thesis. Institut de Police Scientifique et de Criminologie, Université de Lausanne, 

Lausanne, Suisse, 1996. 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 1: The Latent Print Examination Process and Terminology 

3 

Figure 1.1: The Latent Print Examination Process Map
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 1: The Latent Print Examination Process and Terminology 

4 

1.1.1 Analysis 

Analysis refers to the initial examination of a friction ridge impression. By inspecting the latent 

print, the examiner gathers information needed to decide whether it is useful for comparison. 

Figure 1.2: Analysis phase of ACE-V 

To determine the print’s value, the examiner considers three levels of detail in the impression. 

Level 1 Detail (L1D) is defined as “ridge flow.”9 Ridge flow often translates to a pattern type in 

a finger or palm, such as a loop, whorl, or arch formation (see Figure 3.1 in Chapter 3); ridge 

flow also includes other information such as relative curvature. Pattern types are class 

characteristics shared by many individuals. Level 2 Detail (L2D) is defined as “ridge path.”10

 

9 Ashbaugh, D. Quantitative-Qualitative Friction Ridge Analysis: An Introduction to Basic and Advanced 

Ridgeology. CRC Press, 1999.

L2D includes, but is not limited to, minutiae, such as ridge endings, bifurcations, or dots. Even 

the absence of minutiae in an area (called an “open field”) can be significant and highly 

discriminating. Level 3 Detail (L3D) is defined as “ridge shapes.” Ridge shapes include the 

edges of ridges (which may appear indented or protruded) and pores (the location of the center of 

10 Ibid.
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5 

the pore, not the size or shape, which can be highly variable within a source).11 Chapter 3, which 

discusses interpreting information in latent prints, provides additional information on the three 

levels of detail and their use in the Analysis phase. 

After considering the details and the distortion, the examiner judges whether the impression is 

suitable for a comparison. If the examiner concludes that the print lacks sufficient detail for a 

comparison, then the examination ends with the determination that the latent print is not suitable 

for a comparison. Otherwise, the examination moves into the Comparison phase. 

1.1.2 Comparison 

In the Comparison phase, the examiner compares the latent print to one or more exemplar prints. 

Information gathered in the earlier analysis of the latent print provides a starting point. A 

comparison of L1D might take only a split second, as when a whorl is present in the latent, but 

an arch is apparent in the exemplar. If there is no exclusion based upon L1D, then the examiner 

continues the comparison. If the examiner finds disagreement with respect to the target group 

that is too extensive to be the result of the distortion noted in the Analysis phase, the examiner 

will exclude the source of the exemplar as the source of the latent. 

Figure 1.3: Comparison phase of ACE-V 

 

11 Roddy, A. and J. Stosz. “Fingerprint Features—Statistical Analysis and System Performance Estimates,” 

Proceedings of the IEEE, 85, no. 9 (1997): 1390 – 1421; Richmond, S. Do Fingerprint Ridges and Characteristics 

Within Ridges Change with Pressure?. Australian Federal Police, Forensic Services, 2004.
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6 

If the initial target group is not found, alternative target groups may be selected. If the examiner 

locates a comparable set of L1D features in the known exemplar, the examiner proceeds to a 

detailed, side-by-side comparison of L2D and possibly L3D. If the examiner concludes that the 

extent of agreement between the two prints satisfies his or her threshold, then the examiner 

proceeds to the Evaluation phase. 

Figure 1.4 displays a latent print (in the middle) and two very similar exemplar prints from 

monozygotic (identical) twins. One twin is the source of the latent print. These images were used 

in an unusually difficult inter-laboratory comparison in 1995. 

Figure 1.4: A latent print and exemplar prints12

 

12 Images reproduced and adapted with permission of Collaborative Testing Services. 
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1.1.3 Evaluation 

Figure 1.5: Evaluation phase of ACE-V 

In the Evaluation phase, the examiner makes the ultimate decision regarding source attribution. 

Traditionally, three possible findings have been available. First, the examiner can make an 

“individualization” or “identification.” Section 1.2 defines these terms and describes another 

type of source attribution. Second, the examiner can categorically exclude the latent print by 

determining that the exemplar print and the latent do not match and cannot share a common 

source. Finally, the examiner can determine that the information available is inadequate to 

warrant a conclusion. In that event, the examiner would state that the comparison was 

“inconclusive” and would provide no additional information about the chances that the two 

prints share a common source. 

The thresholds for these decisions can vary among examiners and among forensic service 

providers. Some examiners state that they report identification if they find a particular number of 

relatively rare concurring features, for instance, eight or twelve. Others do not use any fixed 

numerical standard. Some examiners discount seemingly different details as long as there are 

enough similarities between the two prints. Other examiners practice the one-dissimilarity rule, 

excluding a print if a single dissimilarity not attributable to perceptible distortion exists. If the 

examiner decides that the degree of similarity falls short of satisfying the standard, the examiner 

can report an inconclusive outcome. If the conclusion is that the degree of similarity satisfies the 

standard, the examiner reports an identification.
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1.1.4 Verification

Figure 1.6: Verification phase of ACE-V 

In the ACE-V acronym, V stands for Verification. Verification procedures vary among forensic 

service providers. At one extreme, the verifier, presented with the first examiner’s work, assesses 

the original conclusion. At the other extreme, the verifier, blinded to the initial examination, 

performs an independent examination. 

1.1.5 Limitations and Concerns about ACE-V 

At every step in the ACE-V process, human factors can affect the outcome. Latent print 

examiners rely heavily on their training and experience to make the required judgments. 

Subjectivity is an inextricable part of the process. In the Analysis phase, for example, accurate 

identification of the characteristics that make prints of value depends on the examiner’s 

knowledge, training, and experience. Likewise, in the Comparison phase, variable factors, such 

as the elasticity of skin and uneven pressure, mean that there will never be perfect congruence 

between two prints, even if they originate from the same source. The examiner must resolve the 

question of whether there is sufficient agreement “within tolerance.” As Chapter 3 points out, the 

examiner at least implicitly relies on a sufficiency threshold to resolve that question, and in 

setting this threshold, the examiner draws on professional knowledge and experience. There is 

little research at present that provides objective metrics for determining these tolerances.
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Of course, the mere existence of subjective elements does not make the process unreliable or 

invalid. Humans can perform many tasks involving subjective judgments quite accurately and 

consistently. For example, by holding a heavy book and a much lighter one in each hand, most 

people can subjectively—but correctly—tell which is heavier. Thus, the mere presence of 

subjectivity is not a valid criticism of the technique, but it does mean that issues related to human 

factors can be especially salient to the outcome. 

Although ACE-V is a systematic process, meaning that the examination proceeds in an orderly 

and logical fashion, this does not, by itself, demonstrate that the results are accurate and 

reproducible. In 2009, a committee of the National Research Council (NRC) stated that ACE-V 

is “a broadly stated framework for conducting friction ridge analyses. However, this framework 

is not specific enough to qualify as a validated method for this type of analysis. ... Merely 

following the steps of ACE-V does not imply that one is proceeding in a scientific manner or 

producing reliable results.”13 Additional study is required to ascertain precisely how well 

examiners using the process perform under either controlled conditions or in casework, and 

Chapter 2 describes several possible approaches to developing such information. 

Although many in the latent print community describe the ACE-V process as a scientific method 

(see Chapter 6), the issue is not the label that can or should be attached to the process with 

respect to human factors. ACE-V is a systematic, skill-based, and widely used process for 

determining whether two impressions have a common origin. ACE-V designates a logical 

sequence for a complex process of judgment, but ACE-V itself does not provide substantive 

guidance about standards to be applied within this sequence. Therefore, even though two 

examiners might both assert (correctly) that they are using ACE-V, they may be employing 

different cognitive processes. Those differences create opportunities for human factors to come 

into play. 

1.2 The Meanings of “Bias” and “Error”

The issues of bias and error are critical to assessing the role of human factors in latent print 

analysis. Those terms are described in detail here, and they are referred to throughout this report. 

1.2.1 Bias 

The term “bias” has many meanings. This report discusses the term as it is used in three 

disciplines. In law, “bias” refers to a witness’s partiality toward one party (or against another) as 

a result of financial, emotional, or other interests or attitudes. The law of evidence does not 

expect all witnesses to be unbiased. Rather, it relies on the disclosure of the biasing interests or 

attitudes through cross-examination, a procedure that is effective primarily in exposing gross 

motivational biases (see Chapter 6). 

In statistics, “bias” refers to the extent to which an average statistic departs from the parameter it 

is estimating or to the extent to which measurements on individual units systematically depart 

 

13 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009, p. 142.
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from the true values. Errors from chance will cancel each other out in the long run; those from 

bias will not (see Chapter 2). 

In psychology, “cognitive bias,” which is addressed throughout this report, is a general term for 

“many observer effects in the human mind, some of which can lead to perceptual distortion, 

inaccurate judgment, or illogical interpretation.”14 Social and cognitive psychologists have 

identified many sources of cognitive bias, including “information-processing shortcuts 

(heuristics), motivational factors, and social influence.”15 

One type of cognitive bias, called confirmation bias, “is perhaps the best known and most widely 

accepted notion of inferential error to come out of the literature on human reasoning.”16

Confirmation bias “connotes the seeking or interpreting of evidence in ways that are partial to 

existing beliefs, expectations, or a hypothesis in hand.”17 It is “a proclivity to search for or 

interpret additional information to confirm beliefs and to steer clear of information that may 

disagree with those prior beliefs.”18 “One may be selective in seeking or interpreting evidence 

that pertains to a belief without being deliberately so, or even necessarily being aware of the 

selectivity.”19 

Observers’ expectations have been shown to influence judgment in a broad range of tasks.20

Especially when confronted with ambiguous stimuli, people tend to see what they hope or expect 

to see. Thus, in a clinical trial of an experimental drug, the failure to blind the clinicians 

evaluating the health of the patients as to whether each patient received the experimental drug or 

the placebo would be regarded as a serious methodological flaw. This knowledge would create a 

bias toward a finding of efficacy. Recognition of this cognitive bias in no way impeaches the 

researcher’s integrity and dedication to learning the truth. It simply means that, on average, the 

measurements the researcher makes could well be shifted systematically from the true values, 

creating a statistical bias. 

As explained in Chapter 3, some information about the origin of a latent print can facilitate 

accurate results, but other contextual information can produce confirmation bias.21

 

14 Kahneman, D. and A. Tversky. “Subjective Probability: A Judgment of Representativeness.” Cognitive 

Psychology, 3 (July 1972): 430.

 Extraneous 

information can influence people acting in good faith and attempting to be fair interpreters of the 

evidence. For example, radiographers may read X-rays differently if they know the patient’s 

15 Ibid.

16 Evans, J. Bias in Human Reasoning: Causes and Consequences. Psychology Press, 1989, p. 41. 17 Nickerson, R. “Confirmation Bias: A Ubiquitous Phenomenon in Many Guises.” Review of General Psychology, 2 

(1998): 175.

18 Budowle, B., M. Bottrell, S. Bunch, et al. “A Perspective on Errors, Bias, and Interpretation in the Forensic 

Sciences and Direction for Continuing Advancement.” Journal of Forensic Sciences, 54 (July 2009): 803.

19 Nickerson, op. cit., p. 176. 20 See Miller, L. “Procedural Bias in Forensic Science Examinations of Human Hair.” Law and Human Behavior, 

11, no. 2 (June 1987): 157; Nickerson, op cit.; and Risinger, D., M. Saks, W. Thompson, et al. “The Daubert/Kumho

Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation and Suggestion.” California 

Law Review, 90, no. 1 (January 2002). 21 See, e.g., Saks, M., D. Risinger, R. Rosenthal, et al. “Context Effects in Forensic Science: A Review and 

Application of the Science of Science to Crime Laboratory Practice in the United States.” Science and Justice, 43, 

no. 2 (April – June 2003): 77.
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clinical history; 27 doctors may 

assess a patient differently in a drug 

trial if they know whether the 

patient is receiving the experimental 

drug or a placebo;28 and a consumer 

may express different taste 

preferences in response to food 

labels or knowledge of the 

ingredients included.29 “Contextual 

bias” occurs when “the forensic 

scientist uses other evidence to 

believe that the specific evidence 

being analyzed is related to a 

particular reference sample(s)”30

and when the contextual 

information prompts a biased 

selection or weighting of the 

features in the samples. 

In short, “bias” can be a loaded 

term, as when people speak of 

personal bias, racial bias, gender 

bias, cultural bias, media bias, 

 

22 E.g., Nickerson, op cit. 23 For a review, see Dror, I. and R. Rosenthal. “Meta-Analytically Quantifying the Reliability and Biasability of 

Forensic Experts.” Journal of Forensic Sciences, 53 (July 2008): 900. See also Dror, I. and S. Cole. “The Vision in 

‘Blind’ Justice: Expert Perception, Judgment, and Visual Cognition in Forensic Pattern Recognition.” Psychonomic 

Bulletin & Review, 17 (2010): 161. 24 Pronin, E. “Perception and Misperception of Bias in Human Judgment.” Trends in Cognitive Science, 11 (January 

2007): 37.

25 Dror, I. “The Paradox of Human Expertise: Why Experts Can Get It Wrong.” In The Paradoxical Brain, edited by 

N. Kapur. Cambridge University Press, 2011; and Busey, T. and I. Dror. “Special Abilities and Vulnerabilities in 

Forensic Expertise.” In The Fingerprint Sourcebook. National Institute of Justice, 2011.

26 E.g., McClelland, J. and D. Rumelhart. “An Interactive Activation Model of Context Effects in Letter Perception: 

Part 1, An Account of Basic Findings.” Psychological Review, 88 (September 1981): 375; and Wilson, T. and 

N. Brekke. “Mental Contamination and Mental Correction: Unwanted Influences on Judgments and Evaluations.” 

Psychological Bulletin, 116 (July 1994): 117. 27 See, e.g., Tape, T. and R. Panzer. “Echocardiography, Endocarditis, and Clinical Information Bias.” Journal of 

General Internal Medicine, 1, no.3 (1986): 300; Schreiber, M. “The Clinical History as a Factor in Roentgenogram 

Interpretation.” The Journal of the American Medical Association, 185 (1963): 137; Doubilet, P. and P. Herman. 

“Interpretation of Radiographs: Effect of Clinical History.” American Journal of Roentgenology, 137, no. 5 (1981): 

1055; and Potchen, E., J. Gard, P. Lazar, et al. “The Effect of Clinical History Data on Chest Film Interpretation: 

Direction or Distraction?” Investigative Radiology, 14 (1979): 404.

28 Levine, R. Ethics and Regulation of Clinical Research. 2nd ed. Yale University Press, 1986; and Shultz, K. and D. 

Grimes. “Blinding in Randomized Trials: Hiding Who Got What.” Lancet, 359 (February 2002): 696. 29 Allison, R. and K. Uhl. “Influence of Beer Brand Identification on Taste Perception.” Journal of Marketing 

Research, 1 (1964): 36; Nevid, J. “Effects of Brand Labeling on Ratings of Product Quality. Perceptual and Motor 

Skills, 53 (1981): 407; Palmer, S. “The Effects of Contextual Scenes on the Identification of Objects.” Memory and 

Cognition, 3 (1975): 519; and Lee, L., S. Frederick, and D. Ariely. “Try It, You’ll Like It: The Influence of 

Expectation, Consumption, and Revelation on Preferences for Beer.” Psychological Science, 17 (2006): 1054.

30 Budowle, Bottrell, Bunch, et al., op. cit., p. 803.

Box 1.2: Misconceptions about “Bias” in Science

Cognitive scientists and psychologists have observed cognitive 

bias in hundreds of scientific studies across dozens of 

domains.22 Research has also demonstrated its existence in 

latent print examination such as when one examiner, presented 

with consistent evidence in different biasing contexts, has been 

shown to reach different conclusions.23 Much of the work in 

latent print examination depends on judgment and decisionmaking. In many scientific fields, such judgments are

recognized as subjective and vulnerable to contextual biases.

Within the forensic science community, some people still lack 

an understanding of what bias is and how best to address it.24

Often, cognitive bias is treated as an ethical issue or as an 

issue that will resolve once someone is aware of the problem. 

However, the cognitive process used when gaining experience 

(e.g., using schemas, chunking information, automaticity, and 

more reliance on top-down information) in itself opens the 

practitioner to vulnerabilities, including bias, tunnel vision, 

lack of flexibility, and selective attention.25 Cognitive bias 

results from computational trade-offs carried out in the brain 

and is not a conscious act or an act that can be avoided at 

will.26 
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political bias, and so on. However, this is not the type of bias with which this report is concerned. 

Although there have been occasional cases of conscious bias—indeed, outright fraud—in 

forensic science31 (as in all sciences and professions), cognitive bias is far more subtle and 

usually unknown to the observer. Just how often such bias produces incorrect findings is difficult 

to say,32 but “the possibility of biases influencing the decision-making process of examiners” 

cannot be dismissed.33 

The issue of cognitive bias is therefore one important topic in the study of human factors in 

friction ridge impression examination. Research on expectancy effects in latent print 

identification is limited.34 However, being consistent with widely accepted psychological 

phenomena, this research has prompted proposals for blinding forensic examiners to the origin of 

samples being compared with each other35 and for using multiple exemplars in comparisons.36

Likewise, blind verification shields the verifying examiner from contextual bias that might 

otherwise affect the outcome in difficult cases. The Noblis-FBI experiment, discussed in Chapter 

2, indicated “that blind verification of exclusions could greatly reduce false negative errors.”37

Taking the human factors perspective, an agency might wish to adopt one or more of these 

systemic changes rather than simply warning examiners to do their best not to be influenced by 

potentially biasing information.38

1.2.2 Error

Like “bias,” the word “error” has a multitude of possible meanings. This report addresses the 

relationship between human factors and the two concepts of error outlined in Chapter 2—

procedural error and outcome error. Procedural error refers to departures from a prescribed 

procedure. The failure of a technician to calibrate an instrument for measuring breath alcohol 

concentration as frequently as regulations prescribe, for example, is a procedural error. It 

 

31 E.g., Giannelli, P. “Independent Crime Laboratories: The Problem of Motivational and Cognitive Bias.” Utah Law 

Review, 247 (2010): 251.

32 Langenburg, G., C. Champod, and P. Wertheim. “Testing for Potential Contextual Bias Effects During the 

Verification Stage of the ACE-V Methodology When Conducting Fingerprint Comparisons.” Journal of Forensic 

Sciences, 54 (May 2009): 571 – 82 (concluding that blind verification may be most useful for exclusions). 33 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Strengthening Forensic Science in 

the United States: A Path Forward, Position Statement. Scientific Working Group on Friction Ridge Analysis, 

Study and Technology, 2009; U.S. Department of Justice, Office of the Inspector General. A Review of the FBI’s 

Handling of the Brandon Mayfield Case (Unclassified and Redacted). U.S. Department of Justice, 2006; Stacey, R. 

“A Report on the Erroneous Fingerprint Individualization in the Madrid Train Bombing Case.” Journal of Forensic 

Identification, 54, no. 6 (2004): 706; and Moses, K. “Anatomy of Error.” Presented at International Association for 

Identification 89th International Educational Conference, St. Louis, Missouri. August 2004. 34 Dror and Cole, op. cit., p. 161; Dror, I., D. Charlton, and A. Peron. “Contextual Information Renders Experts 

Vulnerable to Making Erroneous Identifications.” Forensic Science International, 156, no. 1 (2006): 74 – 78; Dror, 

I. and D. Charlton. “Why Experts Make Errors.” Journal of Forensic Identification, 56, no. 4 (2006): 600 – 16; Dror 

and Rosenthal, op. cit.; and Langenburg, Champod, and Wertheim, op. cit.

35 Krane, D., S. Ford, J. Gilder, et al. “Sequential Unmasking: A Means of Minimizing Observer Effects in Forensic 

DNA Interpretation.” Journal of Forensic Sciences, 53 (2008): 1006. 36 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 123. 37 Ulery, B., A. Hicklin, J. Buscaglia, et al. “Accuracy and Reliability of Forensic Latent Fingerprint Decisions.” 

Proceedings of the NAS. 2011.

38 Following the misidentification of Brandon Mayfield as a Madrid train bomber, for instance, the Federal Bureau 

of Investigation (FBI) implemented blind verification in some cases. U.S. Department of Justice, Office of the 

Inspector General, op. cit.; Stacey, op. cit.; and Moses, op. cit.
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increases the risk of an error in the actual measurements,39 but this risk might not be realized; the 

instrument could remain correctly calibrated during the period in question and thus be no more 

likely to err than it would have if the technician had followed the proper calibration schedule. 

Whether or not the measuring instrument is calibrated in the prescribed manner, it is unlikely to 

give perfectly accurate results. Some measurements will be above the true value, some below it. 

For nominal variables (involving categories, such as the ABO types of blood), measurement 

error usually is called misclassification or classification error.40 

When human beings make comparisons, they also engage in a form of measurement. Visually 

determining that one source of light is bright and another dim, or that one object is large and 

another small, are examples of classifications by a human system for sensory measurement. 

Likewise, the human examiner following the ACE-V process acts as a measuring instrument, and 

the examination of two friction ridge skin impressions is a form of categorical measurement or 

decision-making. An examiner who reaches a conclusion that two impressions of friction ridge 

skin do or do not match is making a binary classification, and it might be a misclassification or 

outcome error. If the exclusion or inclusion corresponds to the true state of affairs, there is no 

such outcome error. A judgment of an exclusion when the two impressions come from the same 

individual’s skin is a false exclusion (a false negative). A declaration of a match when the two 

impressions come from different individuals is a false inclusion (a false positive). Chapter 3 

develops these ideas further. 

1.2.3 Identification: Inclusions and Exclusions

Forensic scientists are sensitive to the breadth of the word “identification.” It can mean placing 

an item in a large class, as in “I identified this automobile as a red Buick.”41 It also can mean 

associating a trace with a single possible source, as when a latent print examiner reports, “I 

identified the latent print as having been made by the right ring finger of the defendant.”42

Examinations of features for the purpose of identification can lead to inclusions (for example, the 

suspect’s red Buick is included in the set of automobiles that might have been used by the 

robbers) or exclusions (for example, the suspect’s green Lincoln is excluded as the one used in 

the robbery). As these examples indicate, an inclusion increases the probability that a trace 

originated from a particular source within that set, and an exclusion decreases this probability to 

essentially zero. In short, in forensic science and law generally, identifying information makes an 

association between a source and a trace either more probable or less probable. If the shifted

probability is large enough, it can justify a source attribution. 

 

39 See Flaherty, M. “400 Drunken-Driving Convictions In D.C. Based On Flawed Test, Official Says.” The 

Washington Post, June 10, 2010.

40 Rothman, K., S. Greenland, and T. Lash. Modern Epidemiology. 3d ed. Lippincott, Williams, & Wilkins, 2008, p. 

138.

41 Thornton, J. and J. Peterson. “The General Assumptions and Rationale of Forensic Identification.” Modern 

Scientific Evidence: The Law and Science of Expert Testimony. West Publishing Company, 1997. 42 Ibid. 
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Latent print examiners often use the word “identification” more narrowly, to denote the finding 

of an association at the conclusion of the process known as ACE-V.43 In this more specialized 

vocabulary, an identification is sometimes also referred to as an individualization.44 In general, 

however, forensic “identification” encompasses observations that could narrow the set of 

possible sources of a trace and thus change the probability that the trace originated from a 

particular source within that set, even when there is more than one remaining possible source. 

Whether and when it is appropriate to conclude that the identification procedure establishes that 

the set of possible sources consists of one and only one individual is discussed below in 

connection with the term “individualization.” 

1.2.4 Individualization 

As the discriminating power of the latent print features used to make an identification increases, 

so does the probability that the matching individual is the source. When every possible source 

has different features, and when these differences are detectable, a match in the feature set can 

establish that a specific individual is the source. In this limiting case, when the features in the 

samples have been accurately ascertained, compared, and found to match, the probability that the 

individual in question is the source is one. The identification then has such specificity that it has 

become an “individualization.” 

The classical theory of latent print identification is that individualization is possible regardless of 

how many people could be considered as possible sources. This theory holds that in the 

population of the entire world (both in the distant past and the far future): (1) every finger has a 

unique pattern of ridges and other features that is maintained throughout a person’s lifetime,45

and (2) a well-trained examiner can ascertain when any impression from a finger displays 

enough features to distinguish it from every sufficiently complete and clear impression of every 

other finger. This is a theory of “universal individualization” based on a premise of “general 

uniqueness.”46 

In practice, a universal individualization means that the examiner is confident that if impressions 

from everyone else who ever lived and ever will live could be compared with the latent print, 

then not one would match.47

 

43 E.g., Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standards for Conclusions. 

Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, September 2003.

The individualizing examiner effectively sets the size of the 

44 E.g., Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standard Terminology of 

Friction Ridge Examination (To Replace: Glossary, Version 2.0). Version 3. Scientific Working Group on Friction 

Ridge Analysis, Study and Technology, February 11, 2011. This terminology defines “identification” as 

“individualization” and notes that in other forensic disciplines “this term denotes the similarity of class 

characteristics.”

45 E.g., Peterson, P., C. Dreyfus, M. Gische, et al. “Latent Prints: A Perspective on the State of the Science.” 

Forensic Science Communications, 11, no. 4 (October 2009); Stoney, D. “Measurement of Fingerprint 

Individuality.” In Advances in Fingerprint Technology, edited by Henry C. Lee and R.E. Gaensslen, 327–87. 2nd ed. 

CRC Press, 2001. 46 Kaye, D., D. Bernstein, and J. Mnookin. The New Wigmore, A Treatise on Evidence: Expert Evidence. 2nd ed. 

Aspen Publishers, 2011. “General uniqueness” means that every element of a set is distinguishable from every other 

element. “Special uniqueness” means that a particular element is distinguishable from all others even if not all of the 

remaining elements are each distinguishable. Kaye, D. “Identification, Individualization and Uniqueness: What’s the 

Difference?” Law, Probability & Risk, 8 (2009): 85.

47 Stoney, 2001, op. cit., p. 332.
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population of possible sources to its maximum (the entire population of the earth) regardless of 

the specific circumstances of the case. The individualization process moves from this maximum 

initial population to a decision.48 At the end of the examination process, the quantity of features 

observed in agreement between two objects (without significant discrepancies) is perceived as so 

impressive that the examiner has ruled out the possibility of a coincidental match, whatever 

initial population of sources was involved. This has been described as a “leap of faith.”49 It 

means that the identification of the source is to the exclusion of all other sources. 

In recent years, the classical theory of universal individualization has come under attack in court 

and in the academic literature (see Chapter 6). Some critics of individualization dismiss the first 

premise of global, general uniqueness as unscientific and metaphysical.50 In principle, however, 

belief in uniqueness is compatible with scientific and statistical reasoning.

51 Nonetheless, the fact 

that the surfaces of every individual’s fingers are unique (at a sufficient level of detail) is not, in 

itself, a persuasive argument for universal individualization.52 In a sense, the uniqueness 

argument proves too much, for just as every three-dimensional surface of every finger 

presumably is unique, so is every latent print left on two-dimensional surfaces, even those from 

the same skin.

53 Consequently, 

uniqueness does not guarantee that prints from two different people are always 

sufficiently different that they cannot be confused, or that two impressions made 

by the same finger will also be sufficiently similar to be discerned as coming 

from the same source. The impression left by a given finger will differ every time, 

because of inevitable variations in pressure, which change the degree of contact 

between each part of the ridge structure and the impression medium.54

This takes us to the second proposition underlying the claim of universal individualization. How 

can we know that a skilled examiner can consistently discriminate between pairs of prints that 

come from the same source and pairs that come from different sources when there is substantial 

variation in both types of pairs? The question of the variability of multiple impressions from the 

same source versus inter-source variability is not special to latent print analysis. It is fundamental 

to the recognition of individual sources across the forensic sciences and to signal-detection 

problems in engineering and psychology. In 1979, it prompted an NRC committee to question 

 

48 Biedermann, A., S. Bozza, and F. Taroni. “Decision Theoretic Properties of Forensic Identification: Underlying 

Logic and Argumentative Implications.” Forensic Science International, 177 (2008): 120. 49 Stoney, D. “What Made Us Ever Think We Could Individualize Using Statistics?” Journal of the Forensic 

Science Society, 31 (1991): 197.

50 Saks, M. and J. Koehler. “The Individualization Fallacy in Forensic Science Evidence.” Vanderbilt Law Review, 

61 (2008): 199.

51 Kaye, D. “Probability, Individualization, and Uniqueness in Forensic Science Evidence: Listening to the 

Academies.” Brooklyn Law Review, 75 (Summer 2010): 1163; National Academy of Sciences, National Research 

Council, Committee on DNA Forensic Science: An Update. The Evaluation of Forensic DNA Evidence. National 

Academies Press, 1996, p. 161.

52 Stoney, 1991, op. cit., p. 331.

53 Vanderkolk, J. Forensic Comparative Science: Qualitative Quantitative Source Determination of Unique 

Impressions, Images, and Objects. Academic Press, 2009, p. 195; and Kaye, D. “Questioning a Courtroom Proof of 

the Uniqueness of Fingerprints.” International Statistical Review, 71 (2003): 521. Compare Cole, S., M. Welling, R. 

Dioso-Villa, et al. “Beyond the Individuality of Fingerprints: A Measure of Simulated Computer Latent Print Source 

Attribution Accuracy.” Law, Probability & Risk, 7 (2008): 165. 54 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit. p. 144.
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16 

the ability of spectrographic analysis to provide voiceprints that can be associated with one and 

only one individual.55 Similarly, the 2009 NRC report asks for “studies [that] would accumulate 

data about the intra-individual variability (e.g., how much one finger’s impressions vary from 

impression to impression, or how much one toolmark or signature varies from instance to 

instance) and the inter-individual variability (e.g., how much the impressions of many 

fingerprints vary across a population and in what ways)” to validate the ACE-V process and “to 

attach confidence limits to individualization determinations.”56 To be sure, “examiners are 

trained to recognize the factors that may affect the translation of information [from three 

dimensions to two];”57 yet the fact remains that “none of these variabilities—of features across a 

population of fingers or of repeated impressions left by the same finger—has been characterized, 

quantified, or compared.”58

Despite such misgivings, many fingerprint experts believe that every latent print (of sufficient 

quality, as judged by a human examiner with no predefined, articulable standard for ascertaining 

sufficiency) from a single finger has a degree of similarity to a rolled or plain print that is 

measurably greater than its similarity to every other finger on Earth. To appreciate just how 

ambitious this claim is, suppose that the chance of two latent fingerprints (from two different 

individuals) appearing so similar as to be declared a match is a mere one in one trillion. Because 

the Earth’s population is approximately seven billion people, it might seem that no pair of fingers 

from different individuals now living would match. After all, one in one trillion is two orders of 

magnitude smaller than one in seven billion. However, seven billion individuals give rise to 

immensely more pairs of prints that, by coincidence, could match. All told, there are nearly 25 × 

1018 distinct pairs of individuals to be considered. Individual 1 can be paired with Individuals 2 

through 7,000,000,000 (for seven billion comparisons). Individual 2 can be paired not only with 

Individual 1 but also with Individuals 3 through 7,000,000,000 (for another seven billion 

comparisons).Statistically, the expected number of indistinguishable pairs from different sources 

is the number of possible comparisons times the probability of a match for each comparison. 

This expected number of matching pairs is 25 × 1018 × 10–12 = 25 million. 

Of course, this particular number is hypothetical. Perhaps some prints are so distinctive that the 

probability of confusing them with any print from any other finger is less than one in one trillion. 

The computation could be refined to handle heterogeneity in random-match probabilities, but the 

purpose here is not to estimate any particular number of matching pairs that might exist. It is 

 

55 National Academy of Sciences, National Research Council, Committee on Evaluation of Sound Spectrograms. On 

the Theory and Practice of Voice Identification. National Academies Press, 1979, p. 4. 56 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 184. 57 Peterson, Dreyfus, Gische, et al., op. cit. Compare NAS, NRC, Committee on Identifying the Needs of the 

Forensic Science Community, op. cit., p. 145. 58 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 144. 

SWGFAST, 2009, op. cit. complains that “a significant body of constructive scientific research ... has not been 

adequately reported by the NAS committee.” Yet, the statement cites no such “significant body” of research that fills 

the specific gap in the proof of the individualization hypothesis noted by the NRC report. Peterson, Dreyfus, Gische, 

et al., op. cit. refer to an “FBI Laboratory manuscript in preparation” that finds that “controlled recordings from the 

friction ridge skin have shown that the information contained in friction ridge impressions does translate reliably as 

a true and accurate representation of what appears on the friction ridge skin.” 
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17 

merely to underscore the nearly inconceivable number of pairs of prints that have to be 

considered to establish the premise of universal individualization.59

Given these difficulties, there has been some movement toward using the term 

”individualization” to mean any definitive identification of a single individual as the source of a 

latent print, even one that falls short of universality. The Scientific Working Group on Friction 

Ridge Analysis, Study and Technology has eliminated the global “exclusion of all others” 

language in its glossary60 and plans to do the same in its standards.61 A draft guideline defines 

individualization as “the decision by an examiner that there are sufficient features in agreement 

to conclude that two areas of friction ridge impressions originated from the same source.” 62 As 

to how this decision is made, the next sentence adds, “Individualization of an impression to one 

source is the decision that the likelihood the impression was made by another (different) source 

is so remote that it is considered as a practical impossibility.”63 

To some extent, however, the new definition begs the question of how the examiner knows that 

the probability that the “impression was made by another (different) source” is practically zero. 

Is the rationale that individualization is still universal, applying as a “practical” matter to 

astronomical numbers of possible pairs? If the “practical” judgment remains based upon the 

classical theory of universal individualization, then an individualization is still a statement that 

the examiner has excluded everyone else in the world as the source of the latent print. 

Perhaps the new form of “individualization” is simply a source attribution based upon an 

examiner’s training and experience with two sets of paired latent and exemplars in which the 

origin of the prints is known. One set consists of all pairs of latent and exemplar prints known to 

the examiner to have come from the same fingers (mates). The other set consists of all pairs 

known to the examiner to have come from different fingers (nonmates). An examiner might 

conclude that the prints being compared are more similar than any pair of nonmates ever 

encountered, and that they are comparable in similarity to the known mates previously 

experienced. If so, this examiner would regard the pair as originating from the same individual. 

We can designate this approach as the mate-nonmate theory of source attribution.64 It assumes 

that the difficulty of classifications in the previously experienced sets of mated and nonmated 

prints are comparable to all those that ever will be encountered in casework.65

 

59 For other discussions of this classic “Birthday Problem” in probability theory and forensic science, see, for 

example, NAS, NRC, Committee on DNA Forensic Science: An Update, op. cit., pp. 137, 161, 165; Page, M., J. 

Taylor, and M. Blenkin. “Uniqueness in the Forensic Identification Sciences—Fact or Fiction?” Forensic Science 

International, 206 (2011): 12, 1415. 60 SWGFAST, 2011, op. cit. 61 Butt, L. Letter from the Chairman, Scientific Working Group on Friction Ridge Analysis, Study and Technology. 

In Regards to: Position Clarification. June 29, 2010. Accessed June 3, 2011. http://www.swgfast.org/CommentsPositions/SWGFAST_NAS_Position_Clarification.doc.

62Scientific Working Group on Friction Ridge Analysis, Study and Technology. Draft for Comment: Standards for 

Examining Friction Ridge Impressions and Resulting Conclusions (To Replace: Friction Ridge Examination 

Methodology for Latent Print Examiners, Version 1.01, and Standards for Conclusions, Version 1.0). Version 1.0. 

Scientific Working Group on Friction Ridge Analysis, Study and Technology, August 2010, p. 4. 63 Ibid., p. 5.

64 Association of Firearm and Tool Mark Examiners. Theory of Identification as it Relates to Toolmarks. 5th ed., 

ver. 5.070207. 2007.

65 Although thinking about the features of mated versus nonmated prints might describe how the examiner thinks (at 

some level), it does not respond to the criticism that it is difficult to say how much confidence one can place on 
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18 

Another possible route to identification that also does not rest on the theory of universal 

individualization has been called “local individualization” because it only claims that the source 

is very probably unique within a particular population that is much smaller than the entire human 

race.66 Local individualization is the assertion that a particular individual within a set of 

plausible suspects is the source of a latent print. This set might be enumerated (a “closed” list of 

suspects); alternatively, it might not be subject to explicit enumeration (the list is “open” even 

though it might be limited by geography or other factors). For example, the relevant population 

might be every resident of a dormitory who was in the dormitory on a given night (“closed”), or 

it might be everyone in a city (“open”). In a local individualization, the examiner concludes that 

the latent print came from one source even if he has not examined the prints of everyone else in 

this local population. 

In Chapter 3, the Working Group recommends against presenting a latent print identification as 

meaning that the source of the exemplar is the source of the latent print to the exclusion of all 

other individuals in the world. However, the members of the Working Group have varying 

opinions as to whether the practice of making source attributions based on the mate-nonmate 

theory or the local-individualization theory is appropriate. Chapter 6 therefore describes 

alternatives to source-attribution testimony without endorsing any of them. 

In sum, the term “identification” is not necessarily synonymous with “individualization.” As a 

general matter, “identification” refers to the association, to some degree of probability, of a trace 

to a source. (The operation of probability theory in this context is explained in the next section.) 

One type of identification is the attribution of a trace to a single source (a source attribution). In 

latent print work, source attributions have traditionally rested on a theory of universal 

individualization. In this framework, an individualization is a statement that a single individual 

must be the source of the trace because no other individual in the world could have produced 

such a trace. Source attributions also can rest on less extreme theories of why the identified 

individual is, very probably, the source, and evidence that does not warrant a source attribution 

also can be useful in investigations and prosecutions. 

1.3 Probability

In describing the nature of error (Chapter 2), the interpretive process of ACE-V (Chapter 3), 

emerging technologies (Chapter 4), and courtroom testimony (Chapter 6), this report uses terms 

and concepts from the theory of probability. Indeed, the previous section describes a source 

attribution as a statement that a particular object or individual is “very probably” the source of a 

trace. This section provides definitions of several of the terms used in theory of probability and 

indicates more fully how source attribution relates to probabilities.67

 judgments made in this fashion if “[n]one of these variabilities—of features across a population of fingers or of 

repeated impressions left by the same finger—has been characterized, quantified, or compared.” NAS, NRC, 

Committee on Identifying the Needs of the Forensic Science Community, op. cit.

66 The logic of “local individualization” and “specific uniqueness” is described more fully in Chapter 6, in Kaye, 

Bernstein, and Mnookin, op. cit., and in Kaye, 2009, op. cit. 67 For more extensive discussions, see, for example, Aitken, C. and F. Taroni. Statistics and the Evaluation of 

Evidence for Forensic Scientists. 2nd ed. John Wiley & Sons, 2004; Kaye, Bernstein, and Mnookin, op. cit.; and 
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19 

Probability is a number between zero and one. A probability of zero means that a proposition is 

definitely false. A probability of one means that a proposition is certainly true. In the empirical 

sciences, absolute certainty in unattainable, although some propositions, such as the claim that 

the Earth orbits the Sun, have probabilities very close to one. 

Probability often is expressed as a percentage. Thus, a 60% probability and a 0.6 probability are 

the same thing. Another way to describe uncertainty is with odds. If the probability that a 

particular baseball team will win the World Series is 60%, the odds are 60 to 40 (or, 

equivalently, 1.5 to 1). 

To place the findings and inferences of forensic scientists in a probabilistic framework, it is 

necessary to distinguish between data or observations on the one hand, and hypotheses on the 

other. That a specific finger is the source of an impression is a hypothesis. The observed features 

in a pair of fingerprints are data. The data can make the hypothesis more probable or less 

probable than it otherwise would be. The probability before obtaining particular data is known as 

the prior probability. The probability after considering the data is known as the posterior 

probability. 

The precise relationship between the prior and posterior probability is given by a formula known 

as Bayes’s rule. The rule tells us how to update the prior probability in light of the data. When 

there are only two possible hypotheses to consider—such as the hypothesis that two impressions 

come from the same fingers and the competing hypothesis that they come from different 

fingers—the increase or decrease in the probability depends on a single factor, called the 

likelihood ratio. Specifically, the posterior odds are the prior odds multiplied by the likelihood 

ratio (see Box 1.3 for examples). The likelihood ratio thus measures the strength of the evidence. 

A large likelihood ratio means that the evidence is powerful: it raises the odds by a large factor. 

The likelihood ratio is just the probability of the data when one hypothesis is true compared to 

(divided by) the probability of the data when the competing hypothesis is true. For example, 

when the features in a latent print and an exemplar are ten thousand times more probable for 

mates than nonmates, the likelihood ratio is ten thousand. Observing these features boosts the 

prior odds for identity (whatever they may be) by a factor of ten thousand. In principle, at least, 

an examiner could estimate the likelihood ratio subjectively or could compute it using a 

statistical model (see Chapters 3, 4, and 6).

 Robertson, B. and G. Vignaux. Interpreting Evidence: Evaluating Forensic Science in the Courtroom. John Wiley & 

Sons, 1995.
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20 

Box 1.3: Probabilities, Likelihood Ratios, and Individualization

The term “individualization” can be given various probabilistic interpretations. The traditional notion of 

universal individualization means that the probability of finding another matching exemplar (if exemplars 

existed for everyone in the world) is essentially zero. However, probability theory shows how evidence 

that is not individualizing in this traditional sense still can be extremely powerful.

As indicated in the text, probabilities can be assigned to two different hypotheses: (1) that two 

impressions come from the same finger (s), and (2) that they come from different fingers (d). If Pe|s

denotes the probability of the observations (the evidence from the latent print examination) when the 

prints are from the same source, and Pe|d represents the probability when they are from different sources, 

then a simple measure of the extent to which the observations support the former hypothesis over the 

latter is the likelihood ratio, LR = Pe|s / Pe|d. 

According to Bayes’s rule, posterior odds = LR × prior odds. Suppose the likelihood ratio is one million, 

meaning that an apparent match is one million times more probable if the prints come from the same 

source than if they come from different sources. Although this likelihood ratio seems extremely high, if 

we assume for the sake of argument that all residents of New York City were equally likely to have made 

an impression, then the odds of s to d change from one to eight million (before considering the evidence) 

to one to eight (after considering the evidence). 

For suspect populations of various sizes, the posterior odds of identity for evidence with this likelihood 

ratio are as follows:

Population size Posterior odds of probability 

(LR = 1,000,000)

The world (~7,000,000,000) 1:7,000

United States (~300,000,000) 1:300

New York City (~8,000,000) 1:8

Colorado Springs (~400,000) 2.5:1

Walla Walla (~30,000) 33:1

A college dormitory (~200) 5,000:1

Table 1.2: Posterior odds of identity for evidence with a likelihood ratio of 1,000,000 in populations in 

which everyone has the same prior odds on being the source of a latent print

An examiner who makes a source attribution is giving an opinion that the posterior probability is 

practically 1 (100%). 

1.4 Summary

This chapter defines various terms and concepts that are central to the assessment of latent print 

evidence. In particular, it describes the steps of the ACE-V process as currently practiced and 

understood by the latent print examination community and discusses how exclusions and 

identifications are fundamentally statements of probabilities. Because humans conduct the 

process, human factors can influence the outcome of an examination. Bias and error can occur in 

any process for making comparisons and drawing inferences. In the context of latent print 

examination, they can play a role in the final decision made by an examiner. Many other human 

factors are at play in the latent print work environment, as addressed in the chapters that follow. 
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Chapter 2: Human Factors and Errors 

21 

Chapter 2: Human Factors and Errors

Human beings, in all lines of work, make errors. Errors can be prevented by 

designing systems that make it hard for people to do the wrong thing and easy for 

people to do the right thing. Cars are designed so that drivers cannot start them 

while in reverse because that prevents accidents. Work schedules for pilots are 

designed so they don’t fly too many consecutive hours without rest because 

alertness and performance are compromised.

—To Err Is Human: Building A Safer Health System68

Introduction and Scope

One goal of this chapter on human factors and errors in latent print examination is to explain the 

systems view of human factors. What is true of drivers and pilots—not to mention judges, police 

officers, lawyers, soldiers, and scholars—is also true of forensic scientists and technicians. All of 

us make errors. This report makes no effort to hide this fact. To the contrary, the Working Group 

agrees that the “culture of blame must be broken down, [and] we must systematically design 

safety into processes.”69 Later chapters apply these ideas to matters such as the training and 

working environment of examiners as well as their performance in interpreting evidence and 

reporting and testifying about their findings. 

The other major goal of this chapter is to describe methods for quantifying the risk of errors in 

latent print examinations. Measuring the incidence of errors serves three functions. First, 

studying error is an integral part of science. A basic tenet of experimental science is that “errors 

and uncertainties exist that must be reduced by improved experimental techniques and repeated 

measurements, and those errors remaining must always be estimated to establish the validity of 

our results.”70 What applies to physics and chemistry applies to all of forensic science: “A key 

task ... for the analyst applying a scientific method is to conduct a particular analysis to identify 

as many sources of error as possible, to control or eliminate as many as possible, and to estimate 

the magnitude of remaining errors so that the conclusions drawn from the study are valid.”71 In 

other words, errors should, to the extent possible, be identified and quantified. 

Second, measuring and tracking error rates is part of a comprehensive quality control and 

assurance system. This idea is not new. In the field of medicine, it has been called the “error 

movement,” and it has firm roots in industrial psychology.72

 

68 National Academy of Sciences, Institute of Medicine, Committee on Quality of Health Care in America. To Err Is 

Human: Building A Safer Health System. National Academies Press, 1999, p. ix.

Although it is difficult to 

69 Ibid. 70 Bevington, P. and D. Robinson. Data Reduction and Error Analysis for the Physical Sciences. 3rd ed. McGrawHill, 2002, p. 1. 71 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009, p. 111. 72 See, e.g., NAS, Institute of Medicine, op. cit.; and Hofer, T., E. Kerr, and R. Hayward. “What Is an Error?” 

Effective Clinical Practice, 3 (2000): 261. 
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Chapter 2: Human Factors and Errors 

22 

demonstrate that the medical error movement has improved hospital patient safety in general,73

quantitative analysis can identify factors associated with errors—including preventable ones—

and thus suggest strategies for error reduction.74 Chapter 9 discusses the importance of 

implementing effective systems to detect deviations from desired practices and incorrect 

judgments in latent print casework.

Finally, in the legal system, quantified “error 

rates” have long been a consideration in 

judging the admissibility of findings or the 

weight that should be given to them. 

Quantification not only can lead to 

improvements in the reliability and validity of 

current practices, but it also could assist in 

more appropriate use of the evidence by 

fact-finders. The objective, in other words, is 

improving the “back end” of the system—the 

use of the evidence in investigations and legal 

proceedings. Many court opinions have 

discussed error rates of scientific tests such as 

polygraphy, speaker identification, and latent 

print identification as a consideration affecting 

the admissibility of these tests. To ascertain the 

prospects for useful quantification, however, 

there must be clarity about the meaning of the 

surprisingly ambiguous term “error” as it 

applies to the task of latent print identification. 

It is necessary to consider various ways to 

measure a suitably defined “error rate” that can 

be used to assess the validity of the method and 

conclusions. 

2.1 The Systems View of Errors and Human Factors

The systems view of human error regards errors and adverse events as a function of a system of 

interacting parts, any or all of which could present opportunities for preventing and correcting 

errors. Forensic science evidence results from a complex productive system. A single examiner 

conducts latent print examinations using various technological tools, but more than one 

individual participates in the production process. A detective may provide candidate suspect 

prints, and an examiner may run a search of an automated fingerprint identification system 

(AFIS) that produces both viable matches and nonmatches that initially appear similar. Finally, 

 

73 Landrigan, C., G. Parry, C. Bones, et al. “Temporal Trends in Rates of Patient Harm Resulting from Medical 

Care.” New England Journal of Medicine, 363 (2010): 2124. 74 Macklis, R., T. Meier, and M. Weinhous. “Error Rates in Clinical Radiotherapy.” Journal of Clinical Oncology, 

16 (1998): 551.; and Weingart, S., R. Wilson, R. Gibberd, et al. “Epidemiology of Medical Error.” British Medical 

Journal, 320 (2000): 774. 75 Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

76 Id. at 594.

Box 2.1: Daubert v. Merrell Dow 

Pharmaceuticals, Inc., and “Error Rates”

In Daubert v. Merrell Dow Pharmaceuticals, 

Inc.,75 the Supreme Court wrote that federal courts 

should determine whether contested scientific 

evidence is “scientifically valid.” It listed four 

non-exhaustive factors that trial judges could 

consider in making these determinations. One of 

these factors came from a federal court of appeals 

opinion on spectrographic voice identification that 

relied on laboratory experiments measuring the 

rate of false positives and false negatives. Citing 

this case, the Supreme Court stated, “In the case of 

a particular scientific technique, the court 

ordinarily should consider the known or potential 

rate of error.”76 

The rules of evidence in many states treat “general 

acceptance” in the scientific community rather 

than “scientific validity” as the touchstone for 

admitting scientific evidence. Courts in these 

jurisdictions have treated error rates from 

controlled experiments as a factor that can help 

show whether a technique is generally accepted.
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Chapter 2: Human Factors and Errors 

23 

additional individuals may verify work. Thus, the etiology of errors requires a characterization of 

not only the contributions of each state of the process to potential errors, but also their 

interactions, since interactions among parts of the system can serve to reduce errors or contribute 

to them. Simply blaming errors on individuals is simplistic and unproductive. One must 

appreciate how human actors function in and interact with other components of a more complex 

system.

The “Swiss cheese” model of errors (see Figure 9.2 in Chapter 9),77 which allows classifications 

of various human factors that contribute to errors, provides a framework for identifying 

weaknesses in the examination process. Briefly, this framework involves factors that are specific 

to an individual examiner, those that are features or products of the work environment, and those 

that are the result of failures of supervision and the structure of the organization. This model is 

explained in more detail in Chapter 9. A seminal example of the effects of interactions between 

humans and technology comes from Hutchins,78 who characterized the tools, procedures, 

training, and checklists that allow a cockpit crew, working with tools such as airspeed indicators, 

to ensure that an airplane does not stall on landing approach. The indicators and control surface 

settings provide valuable safety margins and checks, but they can also can lead to crashes if set 

incorrectly. 

Similarly, latent print examination may well benefit from procedures such as verification, but if 

such procedures are implemented improperly, they can lead to a mere illusion of error reduction. 

Not knowing when an examiner has erred makes error reduction difficult. Numerous studies 

have found that without quick and accurate feedback on correct and incorrect judgments, 

experience does not enhance expertise79 and that experts routinely overestimate their skills.80

Weather forecasters are particularly well calibrated; when they report that the chance of rain is 

60%, it rains about 60% of the time. Lawyers and doctors are not so well calibrated; their 

predictions of the outcomes of cases tend to be optimistic.81 The explanation for the difference, 

at least in part, is that meteorologists get frequent, immediate feedback and rewards for correct 

predictions.82 In forensic handwriting analysis, latent print identification, toolmark identification, 

and other pattern and impression evidence comparisons, examiners do not routinely receive such 

prompt and frequent feedback.83

 

77 This model is presented in Reason, J. Human Error. Cambridge University Press, 1990. It is refined in

Wiegmann, D. and S. Shappell. A Human Error Approach to Aviation Accident Analysis: The Human Factors 

Analysis and Classification System. Ashgate Publishing, 2003. 

Under what circumstances would examiners realize that they 

are working with prints that are beyond their current capabilities? If an examiner feels that his 

78 Hutchins, E. “How a Cockpit Remembers Its Speeds.” Cognitive Science, 19 (1995): 265

79 E.g., Bazerman, M. and M. Neale. Negotiating Rationally. Free Press, 1994, p. 102; and Tversky, A. and D. 

Kahneman. “Rational Choice and the Framing of Decisions.” Journal of Business, 59 (1986): 251. 80 Hoffrage, U. “Overconfidence.” In Cognitive Illusions: A Handbook on Fallacies and Biases in Thinking, 

Judgment, and Memory. Psychology Press, 2004; and Lichtenstein, S., B. Fischhoff, and L. Phillips. “Calibration of 

Probabilities: The State of the Art to 1980.” Judgment Under Uncertainty: Heuristics and Biases. Cambridge 

University Press, 1982.

81 Goodman-Delahunty, J., P. Granhag, M Hartwig, et al. “Insightful or Wishful: Lawyers’ Ability to Predict Case 

Outcomes.” Psychology, Public Policy, and Law, 16 (2010): 133. 82 See National Academy of Sciences, National Research Council, Committee on Behavioral and Social Science 

Research to Improve Intelligence Analysis for National Security. Intelligence Analysis for Tomorrow: Advances 

from the Behavioral and Social Sciences. National Academies Press, 2011.

83 Kaye, D., D. Bernstein, and J. Mnookin. The New Wigmore, A Treatise on Evidence: Expert Evidence. 2nd ed. 

Aspen Publishers, 2011.
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Chapter 2: Human Factors and Errors 

24 

abilities far outstrip his colleagues’ and is willing to make identifications that they would not, 

how would such a situation be identified and resolved? Procedures to reconcile differences of 

opinion might only reduce the independence of each examiner without moving the decision 

criterion toward an optimum. 

Thus, procedural changes aimed at error reduction must be devised and examined at a 

system-wide level. These changes must emphasize data collection and feedback to allow both the 

agency and the examiners to adjust their decision criteria and methods. Well-designed

proficiency tests, employed to enhance skills, are one way to supply feedback. Excluding 

unnecessary contextual information that might affect the outcome of an examination is another 

strategy best implemented with an appreciation of how the system works, since such information 

may need to be integrated at later stages without affecting the initial examination. 

Detecting, analyzing, quantifying, and reducing error is difficult, but these efforts are important 

quality assurance steps. To take these steps, however, it is necessary to define terms such as 

“error” precisely. The remainder of this chapter, therefore, analyzes the meaning of “error,” 

elucidates some possible types and sources of error in the Analysis, Comparison, Evaluation, and 

Verification (ACE-V) process, and compares methods for estimating the risk of error in latent 

friction ridge identification as performed by examiners following ACE-V. 

2.2 Errors in Executing a Procedure

When an individual is expected to follow well-defined steps in a procedure, a departure from the 

protocol or a mistake in one of the steps might be designated an error. For example, suppose that 

a forensic service provider requires its examiners to mark the useful features in a latent print 

before making a side-by-side comparison to an exemplar. A particular examiner neglects to do 

so, but correctly determines that the differences between the latent images and the exemplar are 

so extensive and clear that the prints could not have originated from the same source. The 

examiner then correctly excludes the suspect from whom the exemplar came.

This examiner has not erred in the sense of reaching a false conclusion, but the examiner has 

erred in deviating from the prescribed procedure. Identifying such procedural errors (also called 

“process errors” in medicine),84 perhaps through audits of casework, could be valuable even 

when the errors did not lead to a false conclusion. If the procedural step serves a useful function 

in general, then discovering that examiners are not performing the step may warrant corrective 

action. For example, the system might be redesigned so that examiners must sign a checklist as 

they go along to remind them to complete each step in order.85

If an agency has a policy demanding blind verification of identifications, another example of 

procedural error would be providing the verifying examiner with the knowledge that an earlier 

examination conducted by a highly respected colleague resulted in an identification. Such 

policies serve to prevent any “expectancy effect” from influencing the verification (see Chapters 

 

84 Hickner, J., D. Graham, N. Elder, et al. “Testing Process Errors and Their Harms and Consequences Reported 

From Family Medicine Practices: A Study of the American Academy of Family Physicians National Research 

Network.” Quality and Safety in Health Care, 17 (2008): 194. 85 Compare Stevenson, K., S. Gibson, D. MacDonald, et al. “Measurement of Process as Quality Control in the 

Management of Acute Surgical Emergencies.” British Journal of Surgery, 95 (2007): 376.
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1 and 3). In a laboratory that requires blind verification, a nonblind verification would be a 

procedural error. Discovering a large rate of such departures from the established protocol should 

produce an inquiry into what should be done to correct the situation. 

2.3 Errors in Outcomes

Another type of error, an outcome error, contrasts with procedural error. It is closer, but not 

identical, to an “adverse event” in fields such as aviation and medicine86 and relates to reporting 

the wrong conclusions in latent print examination. Bias does not always produce an incorrect 

outcome. For instance, a radar gun that gives readings that are always 2 miles per hour too low is 

biased, but a reading of 45 mph is a good indication that a driver is exceeding the speed limit of 

35 mph (at least when the random error also is small relative to the measured excess of 10 mph). 

In this example, the performance of the measuring device can be compared to the true state of 

affairs—what sometimes is called “ground truth” in biometrics87 or “states of nature” in decision 

theory.88 However, in real-world latent print casework, this true state of affairs is rarely 

available.

Human decision making also can be poorly calibrated or well calibrated in terms of its accuracy 

in ascertaining the true state of affairs. If a latent print and an exemplar come from two different 

individuals, will an examiner (or an initial examiner and a verifier)89 report that the two prints 

match? If the two prints come from the same individual, will the examiner report that they do not 

match? Of the positive identifications made by examiners, what percentage is mistaken? Of the 

exclusions, what percentage is incorrect? Each of these questions leads to a different statistic—

there is no single “error rate” and no single number that gives the “accuracy” of judgments about 

the origin of pairs of prints.90 Moreover, as discussed below, further questions arise when one 

considers an examiner’s determination that a latent print is insufficient to warrant further 

examination or that the further examination is inconclusive. 

The simplest measures of accuracy (or, conversely, error) in categorization arise when there are 

only two categories. Putting aside, for the moment, judgments of “insufficient” or 

“inconclusive,” the examiner reports either that the prints match or that they do not. The same 

kind of binary categorization task is central to many other disciplines.91

 

86 E.g., Hofer, Kerr, and Hayward, op. cit.

Clinical diagnosis, 

predictions of future violence, and signal detection are a few examples. A radar operator may 

87 E.g., Ratha, N., S. Chen, and A. Jain. “Adaptive Flow Orientation-Based Feature Extraction in Fingerprint 

Images.” Pattern Recognition, 28 (1995): 1657. 88 Berger, J. Statistical Decision Theory and Bayesian Analysis. 2nd ed. Springer, 1984, p. 3. 89 For ease of exposition, the explication of the concept of error in inferring identity that follows speaks of a single 

examiner. The final categorization could result from one examiner using the ACE phases of the process (or any 

other process) or from several examiners using ACE-V (or any other process). 90 E.g., Kaye, Bernstein, and Mnookin, op. cit.

91 In the terminology of the 2009 NRC report and statistics and measurement theory generally, latent print 

identification as performed through the steps of ACE-V is an act of classification. To avoid confusing the yes-no 

type of classification for identification in latent print work with ten-print classification systems (such as the Roscher 

system, the Juan Vucetich system, and the Henry system), however, this chapter generally uses the term 

“categorization.” See Allen, M. and W. Yen. Introduction to Measurement Theory. Waveland Press, 2001; Suppes, 

P. and J. Zinnes. “Basic Measurement Theory.” In Handbook of Mathematical Psychology. Wiley, 1963; and 

Rothman, K., S. Greenland, and T. Lash. Modern Epidemiology. 3rd ed. Lippincott, Williams & Wilkins, 2008, p. 

138.
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26 

need to distinguish between a missile launch, on the one hand, and a flock of birds or anything 

else on the other. Signal-detection theory provides a well-developed analytical framework 

involving the probabilities of false alarms (false positives) and missed signals (false negatives).92

The definition of error in this analytical framework is simple. The outcome is judged against a 

true state of the world. An error is a reported categorization that does not report the true state. If 

the radar operator misses the signal of the missile launch (a false negative), or if the operator 

declares an alarm when no missile is in the air (a false positive), then the error will become 

apparent all too soon.93 Table 2.1 summarizes the same two kinds of errors that can arise in 

determining whether a latent print is from the known source of an exemplar. The first column 

lists the examiner’s possible decisions: declare that the prints are so different that the source of 

the exemplar is excluded (abbreviated as –) or declare that the prints are so similar that the 

source of the exemplar is included (an identification, abbreviated as +). The first row lists the 

true states of the world: different source (d) or same source (s). In casework, these states would 

not generally be known. In an experiment or a proficiency test, however, they would be. This 

knowledge makes no difference to the definition of an outcome error, although it affects our 

ability to estimate the conditional error probabilities. In the table, “P( )” stands for “probability 

of.” The vertical bar “|” stands for “given that” or “on the condition that.” 

Different source (d) Same source (s)

Exclusion (–) True negative

Specificity = P(–|d) 

False negative (a miss, type II 

error)

1 – sensitivity = P(–|s)

Identification 

(+)

False positive (false alarm, type I 

error)

1 – specificity = P(+|d)

True positive (a hit)

Sensitivity = P(+|s) 

Table 2.1: Types of errors and correct conclusions in a binary classification task 

In latent print comparisons that lead to only the two outcomes shown in Table 2.1—exclusions 

and identifications—a false negative error is an exclusion when the pair actually originated from 

the same friction ridge skin. Its probability, marked in the upper right-hand corner of the table, is 

P(–|s). In contrast, a false positive probability P(+|d), in the lower left-hand corner of the table, 

measures the chance of an identification when the pair actually did not originate from the same 

source. 

Instead of referring to these two conditional error probabilities, one can refer to two related 

quantities that define the accuracy of the judgment. Sensitivity is the probability of identification 

 

92 Melsa, J. and D. Cohn. Decision and Estimation Theory. McGraw-Hill, 1978; Swets, J. and R. Pickett. Evaluation 

of Diagnostic Systems: Methods from Signal Detection Theory. Academic Press, 1982; and Wickens, T. Elementary 

Signal Detection Theory. Oxford University Press, USA, 2002. 93 When the categorization system maps quantitative scores into binary categories, its performance can be depicted 

as a receiver operating characteristic (ROC) curve. This is a plot of the true positive rate (sensitivity) vs. false 

positive rate (1 – specificity) for a binary classifier system as its discrimination threshold is varied. National 

Academy of Sciences, National Research Council, Committee on Evaluation of Sound Spectrograms. On the Theory 

and Practice of Voice Identification. National Academies Press, 1979, p. 4.
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given that the prints actually come from the same source. These correct outcomes lie in the 

bottom right-hand corner of the table. Specificity is the probability of exclusion given that the 

prints actually came from different sources (upper left-hand corner). 

Sensitivity and specificity are commonly used to appraise the diagnostic value of a test in clinical 

medicine. A pregnancy test that almost always gives a positive result in cases of pregnancy has a 

high sensitivity. On the other hand, a pregnancy test that identifies many women as pregnant 

when they are not has low specificity. That pregnancy test is sensitive to the condition but its 

positive results are not very specific to pregnancy. An ideal diagnostic test is both highly 

sensitive and highly specific, and so is the ideal fingerprint examiner. Encountering a latent and 

an exemplar from the same source, this examiner almost always makes an identification. 

Presented with a latent and an exemplar from different sources, this examiner almost always 

makes an exclusion. 

The important points to be gleaned from Table 2.1 are that (1) each type of error has a 

probability of occurring given the true state of the world (whether known or unknown), and 

(2) the false-positive probability is not generally equal to the probability that the prints are from 

different individuals when an examiner declares a match. The latter is a posterior probability 

(Chapter 1). To make this more concrete, suppose that an experimenter gives an examiner 200 

pairs of prints to examine. A latent and an exemplar comprise each pair. For 100 of the pairs, the 

latent and the exemplar come from different individuals (d); and for the other 100 pairs, the 

latent and the exemplar come from the same individuals (s). The examiner compares the prints in 

each and every pair, and correctly classifies 99 of the former group and 98 of the latter. This 

situation is shown in Table 2.2. Again, these numbers are hypothetical and merely intended to 

illustrate how various measures of accuracy and error are computed. Results from a recent 

experiment are described later in this chapter.

Different source (d) Same source (s)

Exclusion (–) True negatives = 99

Specificity = P(–|d) = 99%

False negatives = 2

1 – sensitivity = P(–|s) = 2%

Identification 

(+)

False positives = 1

1 – specificity = P(+|d) = 1% 

True positives = 98

Sensitivity = P(+|s) = 98%

Table 2.2: Outcomes of a hypothetical experiment that estimates an examiner’s sensitivity and 

specificity

The examiner in this example has performed with a sensitivity of 98% (correct identifications) 

and a specificity of 99% (correct exclusions). Equivalently, the examiner’s false negative and 

false positive rates were 2% and 1%, respectively. 

It is important to understand that these numbers do not translate directly into a probability that an 

identification or an exclusion is correct. The probabilities of a correct identification or exclusion 

are influenced by the proportion of cases in which the pairs of prints actually come from the 

same individuals. Box 2.2 presents a numerical example of how changing the mix of true and 

false pairs changes the probability of a true positive identification.
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Box 2.2: How Prevalence, Sensitivity, and Specificity Affect the Posterior 

Probability of a Correct Positive Identification 

The probability that the examination has correctly classified a pair of prints as identifying the 

individual is the proportion of all those cases in which the examiner has made a positive 

identification that involve true pairs. For example, consider a set of 1,000 pairs of prints that 

includes only 800 true pairs for an 80-20 mix. An examiner with a sensitivity of 98% would 

classify approximately 98% of these 800, or 784, as identifications. But there also are 200 false 

pairs to consider. The examiner with a specificity of 99% would classify approximately 1% of 

these 200, or 2, as identifications. The total number of identifications therefore would be 784 + 2 

= 786. Thus, the examiner would make correct identifications for approximately 784 out of 786 

identifications: P(s|+) = 784/786 = 99.7%. The following table summarizes these calculations:

Number Number + Pr(s|+)

True pairs (s) 800 784

False pairs (d) 200 2

Total 1,000 786 784/786 = 99.7%

Table 2.3: Hypothetical data to show probability of correct identifications in an 80-20 mix

Now suppose that the examiner’s casework consisted of a 10-90 mix of true and false pairs. Of 

the 1,000 cases, 100 are true pairs, and 900 are false pairs. This depresses the value of P(s|+) to 

(100 × 98%) / [(100 × 98%) + (900 × 1%)] = 98 / (98 + 9) = 92%. The examiner’s ability to 

discriminate between a true pair and a false pair has not changed. The sensitivity is still 98%, and 

the specificity is still 99%. However, the expected number of each type of error in the sample of 

casework is different, lowering the probability that a positive identification is correct, as shown in 

the following table:94

Number Number + P(s|+)

True pairs (s) 100 98

False pairs (d) 900 9

Total 1,000 107 98/107 = 92%

Table 2.4: Hypothetical data to show probability of correct identifications in a 10-90 mix

Thus far, we have assumed that the identification process always reaches a conclusion of 

exclusion or identification, and we have described how an experiment could measure the 

sensitivity and specificity of examiners using the ACE-V (or any other) process to reach these 

conclusions. However, examiners have other options. They can declare the latent print (or 

exemplar) to be insufficient for a comparison, or they can make a comparison but designate it as 

 

94 These computations are examples of Bayes’s rule, where the proportion of true pairs in casework is the prior 

probability that a random pair comes from the same source. Compare Parmigiani, G. Modeling in Medical Decision 

Making: A Bayesian Approach. Wiley, 2002, p. 9. In a fully Bayesian analysis, however, the prior probability is 

subjective and need not equal the past frequency. But even if there is no known value, the existence of a prior 

probability that a random pair comes from the same source has to be borne in mind. In that way, examiners are more 

likely to remember that the probabilities of exclusion or identification given a pair of impressions from the same 

source are not the probabilities that a source exclusion or attribution is correct.
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“inconclusive.” Table 2.1 can be expanded with an additional row to account for those possible 

outcomes (Table 2.5). 

Different source (d) Same source (s)

Exclusion (–) True negative

Specificity = P(–|d) 

False negative

1 – sensitivity = P(–|s) 

Identification (+) False positive

1 – specificity = P(+|d)

True positive (a hit)

Sensitivity = P(+|s)

Insufficient or 

inconclusive

Missed an exclusion Missed an identification

Table 2.5: Types of errors and correct conclusions in a binary classification task 

with the option of not deciding

The additional row complicates the computation of error and accuracy rates.95 Should sensitivity 

and specificity be calculated relative to ground truth for all cases presented, or just for those in 

which an examiner reaches a definitive conclusion (an exclusion or an identification)? The 

argument for tossing out inconclusives is as follows: 

When an examiner offers an “inconclusive” opinion about whether two prints 

match, there is a sense in which he has erred. After all, he did not get the answer 

right, and the consequences of this failure may be serious (e.g., missed 

opportunity to exonerate a suspect). However, in the more usual sense of the 

meaning of error, an inconclusive is not an error. It is a pass. An inconclusive 

means that the examiner offers no judgment about whether two prints do or do not 

share a common source.96

Suppose, then, that one agrees that an inconclusive cannot be considered an outcome error (not 

even an outcome error that is less serious than a false identification or a false exclusion). It is still 

not clear whether the inconclusives should be included in the denominators of the proportions for 

true and false positives and true and false negatives. 

The answer may turn on the setting in which the error and accuracy rates will be used. The view 

that inconclusives should not count is appropriate from the perspective of a judge or juror who 

might consider error rates or probabilities to assess the probative value of an identification or an 

exclusion. For that purpose, it does not matter how often the examiner refrains from reaching a 

categorical conclusion. What matters is accuracy in those cases in which the examiner does offer 

an opinion on identification or exclusion. These are the only cases in which an examiner’s 

testimony might lead the jury astray. Testimony that the latent print contained inadequate 

information to reach any conclusion as to the origin of the print occurs less often and should not 

 

95 See Scientific Working Group on Friction Ridge Analysis, Study and Technology. Draft for Comment: Standard 

for the Definition and Measurement of Rates of Errors and Inappropriate Decisions in Friction Ridge Examination. 

Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, February 2011. 96 Koehler, J. “Fingerprint Error Rates And Proficiency Tests: What They Are And Why They Matter.” Hastings 

Law Journal, 59 (2008): 1077.
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propel the jury in any particular direction. Therefore, any calculated error rate presented in a trial 

involving an identification or an exclusion should be based upon the subset of cases in which 

examiners actually make an identification or an exclusion. 

Nevertheless, from the perspective of the police, what matters is all the cases that an examiner 

considers rather than just those in which the examiner ultimately might testify. In terms of 

improving the contribution of the examiner to the investigative process, it is appropriate to 

regard the failure to identify or exclude when the latent print contains adequate information as a 

potentially correctable error. Likewise, deciding that the latent print is of sufficient quality, but 

concluding that the comparison is inconclusive when, in fact, the similarities (or differences) are 

distinct and extensive, also is an error. Whether one regards such errors as outcome or process 

errors (or both), they are important because they might warrant a change in training or 

operational procedures to take fuller advantage of the latent friction ridge data.97 

To help identify undesirable inconclusives, reliability and reproducibility studies could compare 

the performance of examiners in making judgments of sufficiency and conclusiveness. When the 

same examiner reaches the same conclusions (whether right or wrong) in repeated examinations 

of the same set of prints with no recollection of the earlier results, “intra-examiner reliability” is 

high. When different examiners independently studying the same set of prints reach the same 

conclusions, “inter-examiner reproducibility” is high. Table 2.6 uses four categories for the 

outcomes of latent print examinations: identification, exclusion, inconclusive, and insufficient 

(not suitable for comparison). A high number of discrepant judgments signals a need to 

understand what is causing the discordance and perhaps to correct it. 

Examiner 2

Identification Exclusion Inconclusive Insufficient

Examiner 1 

Identification AGREE

Exclusion AGREE

Inconclusive AGREE

Insufficient AGREE

Table 2.6: Concordancy in judgments of two examiners

A related method of spotting problematic judgments uses pairs of prints that are relatively 

complex to examine but that the agency is convinced should result in specific judgments in each 

category. In this situation, there are correct answers (in the judgment of the best experts), and the 

objective is to ensure that all examiners reach these desired outcomes. Table 2.7 shows the 

correct and incorrect outcomes relative to the desired outcomes rather than to ground truth. 

 

97 Because of the differing possible uses of error and accuracy rates, in discussing studies of these rates, this chapter 

gives the results of calculations both with and without inconclusives.
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Desired Outcomes as Determined by Experts

Identification Exclusion Inconclusive Insufficient

Examiner 

Identification CORRECT False positive False positive False positive

Exclusion False negative CORRECT False negative False negative

Inconclusive 

Missed an 

identification

Missed an 

exclusion CORRECT Missed insufficient

Insufficient Missed an 

identification

Missed an 

exclusion

Missed an 

inconclusive CORRECT

Table 2.7: Concordancy with desired outcomes as determined by experts 

The discordant outcomes in Table 2.7 are of varying importance. Many of them would not affect 

the usefulness of the examiner’s findings. For example, if an examiner concludes that the prints 

are insufficient for comparison when the “correct” opinion is that they are worth further study 

but are nonetheless inconclusive, then the examiner did not produce a result that could have 

affected the outcome of that case. Nonetheless, an examiner who is too prone to dismiss samples 

as unsuitable when they are sufficient for comparison but ultimately inconclusive also might be 

too inclined to regard them as insufficient when they would permit an identification or an 

exclusion. These discordant outcomes may not produce outcome errors, and they are not 

amenable to inclusion in “error rates” for ascertaining probative value. But following up on them 

could be important to making the best use of the data and to reducing the risk of actual outcome 

errors.

2.4 Measuring the Prevalence of Error: Prospects and Pitfalls

On occasion, the lures and pressures of the adversarial system, combined with the natural 

tendency of scientists and technicians to be confident in the power of the technology at their 

command and their decision-making abilities, can lead to excessive claims of accuracy. Two 

examples unrelated to friction ridge identification illustrate the phenomenon. First, claims that 

“everyone’s voiceprint is as unique as his fingerprints, and that any skilled technician can 

identify a voiceprint with more than 99% accuracy,”98 prompted the National Research Council 

(NRC) to caution that “the assumption that intra-speaker variability is less than ... inter-speaker 

variability ... is not adequately supported by scientific theory and data.”99 Second, in the initial 

years of DNA testing, expert witnesses claimed that false positive matches were impossible.100

In response, a separate NRC committee reminded them that “laboratory errors happen, even in 

the best laboratories and even when the analyst is certain that every precaution against error was 

taken.”101 

 

98 Kersta, L. As summarized in “The Law: Speak, Voiceprint.” Time. January 10, 1972. 99 NAS, NRC, Committee on Evaluation of Sound Spectrograms, op.cit.

100 For examples, see Kaye, D. “Probability, Individualization, and Uniqueness in Forensic Science Evidence: 

Listening to the Academies.” Brooklyn Law Review, 75 (Summer 2010): 1163. 101 National Academy of Sciences, National Research Council, Committee on DNA Technology in Forensic 

Science. DNA Technology in Forensic Science. National Academies Press, 1992, p. 82.
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Expert witnesses on latent print identification have heeded these admonitions. To be sure, many 

experts once assured courts that the examination process was so rigorous that no competent 

examiner meticulously following the prescribed steps could reach a mistaken conclusion.102

Today, however, many experts understand that insistence on “perfect accuracy,” “no errors,” and 

“a zero error rate”103 for the ACE-V “method itself, if followed correctly ... does not lead to a 

process of method improvement”104 and that these claims “have no scientific basis”105 and “are 

not scientifically plausible.”106 Commentary from the latent print community “acknowledges that 

errors do occur and furthermore that claims of zero error rate in the discipline are not 

scientifically plausible.”107 

But if the rates of various kinds of errors are not zero, how can we know what they are, and what 

use can courts make of the possible estimates? The frequency with which different types of 

errors occur—and even whether meaningful data exist or can be produced to estimate this 

frequency—are subject to differing opinions. In a lengthy review, Cole concluded that “the 

existing data are inadequate to calculate a meaningful error rate for forensic fingerprint 

identification.”108 Pointing to “known cases of fingerprint misattribution” and a 0.8% rate of 

false positives on external proficiency tests, however, he proposed that “the error rate may not be 

trivial.” 109 The NRC committee was more circumspect when it wrote that “there is limited 

information about the accuracy and reliability of friction ridge analyses.”110 In response, the 

Scientific Working Group on Friction Ridge Analysis, Study and Technology insisted that

history demonstrates that the actual error rate in practice is very low. ... Billions of 

comparisons worldwide have occurred over the course of a century with an 

extremely low number of errors. ... Recent studies published in peer-reviewed

journals, although limited, also tend to suggest that the error rate of friction ridge 

examination, when conducted by competent examiners, is very low.111

Likewise, in United States v. Baines,

112

 

102 For examples, see United States v. Baines, 573 F.3d 979, 997-98 (10th Cir. 2009); Government’s Combined 

Report to the Court and Motions in Limine Concerning Fingerprint Evidence, at 22, United States v. Mitchell, 199 F. 

Supp. 2d 262 (E.D. Pa. 2002), aff’d, 365 F.3d 215 (3d Cir. 2004); United States v. Llera Plaza, Crim. No. 98-362-

10, 11, 12, 2002 U.S. Dist. LEXIS 344 (E.D. Pa. Jan. 7, 2002), vacated, 188 F. Supp. 2d 549 (E.D. Pa. 2002).

a former Federal Bureau of Investigation (FBI) 

supervisor testified that the FBI had “made, on average, about one erroneous identification every 

11 years.” Estimating the total number of comparisons made at about 1 million per year, he 

assured the court that the known actual error rate was about one per eleven million comparisons. 

103 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 47.

104 Ibid., p. 143. 105 Zabell, S. “Fingerprint Evidence.” Journal of Law and Policy, 13 (2005): 177.

106NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 143.

107 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Strengthening Forensic Science in 

the United States: A Path Forward, Position Statement. Scientific Working Group on Friction Ridge Analysis, 

Study and Technology, 2009. See also Champod, C. “Fingerprint Examination: Towards More Transparency.” Law, 

Probability & Risk, 7 (2008): 111. 108 Cole, S. “More Than Zero: Accounting for Error in Latent Fingerprint Identification.” Journal of Criminal Law 

and Criminology, 95 (2005): 1033.

109 Ibid. 110 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p.143. 111 SWGFAST, 2009, op. cit. 112 573 F.3d 979, 984 (10th Cir. 2009).
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But the reliance on denominators of millions and “billions of comparisons” has been challenged 

on the grounds that

the chances of uncovering an erroneous identification are remote. Most 

fingerprint identifications are not challenged in court either because the defendant 

pled to some other charge or because the defense did not obtain a second opinion. 

Further, after conviction, the opportunities for innocent persons to obtain new 

evidence and have their convictions reviewed and overturned are still extremely 

rare.113

Historical inquiry is simply not a viable way to estimate how low the false positive rate has been, 

let alone to estimate the size of the false negative rate.

Instead, one might consider using data from five possible sources: non-blind proficiency tests

currently in use; realistic, blind proficiency tests; verifications; random audits of case reports; 

and controlled experiments. These kinds of data vary in their suitability for estimating error rates, 

and all of them have significant limitations. To begin with, proficiency tests designed and 

administered for certification and quality improvement purposes bear little resemblance to actual 

casework. The employees or trainees taking them are not blind to the fact that they are being 

tested, and the samples prepared for certification and quality improvement purposes can be 

different from casework samples. For such reasons, one large proficiency test provider has 

cautioned against using its proficiency test data for calculating error rates. 114 

Second, recognizing that normal proficiency tests are neither designed for nor particularly 

suitable for estimating error rates, some commentators have proposed more realistic, blind 

proficiency testing to produce estimates of error rates for individuals, organizations, or the entire 

profession.115 Truly blind proficiency testing is possible, but implementation on a large scale 

may not be feasible given the logistics and costs.116 For the entire laboratory to be blinded, law 

enforcement authorities must disguise the test so that it appears as a routine case to the target 

laboratory. European DNA laboratories undergo two “blind trials” a year with many samples, but 

these are really “a ‘graded’ interpretation test.”117 The commission that designed the trials 

“seriously considered” but rejected “the setting up of a ‘fake’ or simulated casework situation to 

be distributed among the participants ... [because] this was deemed to be extremely difficult to 

implement from a practical point of view and also to offer no great advantage to the testing 

procedure.”118

 

113 Haber, L. and R. Haber. “Scientific Validation of Fingerprint Evidence Under Daubert.” Law, Probability & 

Risk, 7 (2008): 87. See also S. Cole, op. cit.; Saks, M. “Merlin and Solomon: Lessons From the Law’s Formative 

Encounters with Forensic Identification Science.” Hastings Law Journal, 49 (1998): 1102, note 169.

Thus, if actual error rates are quite small, an impractical number of realistic 

proficiency tests (in which the entire laboratory is blind to the testing) would be required to 

114 Collaborative Testing Services, Inc. CTS Statement on the Use of Proficiency Testing Data for Error Rate 

Determination. Collaborative Testing Services, Inc, March 30, 2010. 115 E.g., Koehler, op. cit. 116 Peterson, J., G. Lin, M. Ho, et al. “The Feasibility of External Blind DNA Proficiency Testing.” Journal of 

Forensic Sciences, 48 (2003): 21. 117 Butler, J. Fundamentals of Forensic DNA Typing. Academic Press, 2010, p. 299. 118 Rand, S., M. Schürenkamp, and B. Brinkmann. “The GEDNAP (German DNA Profiling Group) Blind Trial 

Concept.” International Journal of Legal Medicine, 116, no. 4 (2002): 199.
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produce accurate estimates.

119 Using the upper bound of a confidence interval based upon a 

small sample could grossly overstate the likelihood of an error in a particular case (see Box 

2.3).120

Third, forensic service providers that 

routinely use verifications could compile 

statistics on the outcomes. Because 

verifications are less costly than blind 

proficiency tests, a much larger number 

of observations would be available, 

leading to a more precise estimate. 

However, at best, statistics on the 

outcomes of verifications estimate 

reproducibility rather than validity. That 

two examiners agree does not prove that 

both are correct; that they disagree does 

not tell us which one is correct. 

Consequently, statistics on verifications 

would not estimate false positive or false 

negative probabilities. 

This is not to say that verification 

statistics have no relevance to error 

probabilities. If examiners usually reach 

conflicting results, one can infer that the 

ability to make correct classifications of 

pairs of prints is limited. Establishing 

reproducibility, therefore, is a part of the 

process of validating measurements, but 

concordance between the two examiners 

is a flawed measure even of 

reproducibility if the verifying 

examiner’s judgments are influenced by 

knowledge of the first examiner’s 

opinion. Forensic service providers that conduct a large number of blind verifications, however, 

could contribute to a more complete base of knowledge about the examination process by 

compiling statistics on these verifications. That verifying examiners, proceeding with no 

knowledge of the outcome of the initial examination, almost always reach the same conclusions 

 

119 Champod, op. cit., p. 112; National Academy of Sciences, National Research Council, Committee on DNA 

Forensic Science: An Update. The Evaluation of Forensic DNA Evidence. National Academies Press, 1996.

120 Ibid. 121 Hanley, J. and A. Lippman-Hand. “If Nothing Goes Wrong, Is Everything All Right? Interpreting Zero 

Numerators.” Journal of the American Medical Association, 249 (1983): 1743. 122 Louis, T. “Confidence Intervals for a Binomial Parameter After Observing No Successes.” The American 

Statistician, 35 (1981): 154; Hanley, op. cit. 123 Bickel, P. and K. Doksum. Mathematical Statistics. Holden-Day, 1977. 124 Winkler, R., J. Smith, and D. Fryback. “The Role of Informative Priors in Zero-Numerator Problems: Being 

Conservative Versus Being Candid.” The American Statistician, 56 (2002): 1.

Box 2.3: The Zero Numerator Problem

Suppose that a group of latent print examiners is not 

known to have made any false identifications over a 

long period. One cannot be sure that there have been no 

false positives, because there has been no intensive 

effort to detect any. Over the next decade, therefore, the 

examiners undergo a series of 100 blind proficiency 

tests on prints representative of casework. This situation 

gives rise to the question in the title of a well-known 

article, If Nothing Goes Wrong, Is Everything All Right? 

Interpreting Zero Numerators.

121 A quick answer, 

according to classical statistical theory, is the “Rule of 

Three,” which states that 3/n is a good approximation 

for an upper 95% confidence bound for the probability P

of an outcome of an event when the proportion of the 

outcomes in a large number n of independent trials is 

0/n.

122 Therefore, 3/100 is a conservative estimate of the 

probability of a false positive for these examiners who 

passed the 100 realistic, representative, blind proficiency 

tests involving true positives. 

However, it is a very conservative estimate. It 

corresponds to starting with the belief that P is equally 

likely to be anywhere in the interval between zero and 

one.123 Prior to the proficiency tests, it was plainly 

unrealistic to think that it was just as likely that the 

examiners’ probability of a false positive was greater 

than one-half as it was to have been less than onehalf.124 
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as initial examiners would indicate that the judgments of different examiners are at least 

reproducible. Moreover, whether or not the verifications are blind, the data on initial 

discrepancies could be helpful in identifying individual examiners or situations that merit 

constructive, corrective action. 

Fourth, the outcomes of random audits of completed casework might be used to estimate false 

positive or false negative probabilities. For quality assurance, random technical case audits test 

the entire scope of evidence examination and reporting. Such audits can be conducted internally 

(by the same agency that did the examination) or externally (by an outside entity). These 

technical case audits include a re-analysis of the evidence and an associated evaluation. As with 

proficiency tests, the purpose of conducting technical case audits is to improve laboratory 

performance and to increase reliability and reproducibility. There is an inherent value of a 

program including these audits (regardless of any particular case audit outcomes) that results 

simply from each examiner knowing that some of his work will be re-examined. This knowledge 

may make people more conscientious in their documentation and performance. 

Case audits are designed to detect deviations from ideal, normative, or intended practices. 

Finding these alone makes the audit process useful. The findings can identify specific corrective 

actions (as they relate to the case), or they can identify more general issues, resulting in 

recommendations for improvements (for example, changes in processes or in training methods). 

Audits generally do result in such findings, since all processes can be improved; arguably, if an 

agency performs audits, it should make them rigorous enough for the agency to acquire data on 

areas for improvement. Thus, compilations of technical case audit findings are a potential source 

of valuable information. They provide quantitative data regarding the occurrence of different 

types of deviations from ideal or intended practices. The data can suggest which deviations may 

be occurring systematically, leading to modifications in technical audit procedures or to more 

specific investigations or research.

Technical case audit compilations, however, are not a reasonable way to measure overall latent 

print process performance or to estimate the error rate of a specific latent print process. 

Individual technical audits differ in their criteria, rigor, and areas of concern (as is appropriate 

and consistent with their purpose). Compilations of findings will represent combinations of cases 

with different examiners, different levels of difficulty, and different examination processes. The 

actual causes of problems detected in technical case audits usually cannot be determined. And, 

once again, ground truth, which would be necessary for establishing errors in identifications and 

exclusions, is unknown for audited casework. 

Rather than auditing casework, an expert panel of latent print examiners could conduct its own 

evaluations of a large sample of previous casework (blinded to the earlier outcomes).125

 

125 See SWGFAST, 2009, op. cit. 

The 

results would test the conclusions reached in actual casework. However, the true source of the 

latent prints in these cases would not be known with certainty. The panel’s conclusions would 

have to be accepted as correct if they are to serve as the measure of accuracy in casework. 

Without proof of the panel’s accuracy, the experiment would be subject to the criticism that it 

seeks to prove one unknown by means of another. Although the absence of ground truth 

technically makes this experiment a reproducibility study, the expert panel experiment could be 
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revealing. Studies of the predictive power of screening tests in medicine rely on this 

experimental design when they use a more precise (but still imperfect) test to measure the 

accuracy of the first result. A large number of discordant evaluations would reveal the need for 

further research targeted to ascertaining the sources of the discrepancies. Conversely, high 

concordance rates would support the perception that latent print analysis is a reliable and 

reproducible process as currently practiced. 

Finally, controlled experiments with simulated materials are possible. These could illuminate the 

conditions under which possible errors might occur, could help provide a scientific foundation 

for the validity of the ACE-V process (as practiced by the subjects in the experiment), and could 

supply the kind of error rate information mentioned in Daubert v. Merrell Dow Pharmaceuticals, 

Inc.

126 To determine error rates of a specific type, or for a specific process, one can design an 

experiment that has a consistent process and for which the correct outcomes are known. In this 

way, an error can be detected conclusively (as distinct from a process divergence examined in 

case audits). 

This is the logic that underlies the European collaborative exercises in the DNA field.127 The 

researchers conducting these exercises have found that the overall error rate dropped sharply 

with the introduction of standardized, commercially available DNA testing kits in 1999; that 

“human carelessness is the predominant source of error regardless of the technology used;” that 

these errors take the form of “the transposition of samples, ... albeit never [twice] by the same 

laboratory” and “writing a correct result incorrectly in the summary sheet supplied” but not 

normally used in the laboratory;128 and that the total error rate has stabilized in the range of 0.4% 

to 0.7%.129 The researchers’ conclusions indicate the value of experiments like these: “During 

the development of the trials over the last decade since the introduction of STRs [short tandem 

repeats], many lessons have been learnt which have led to improvements not only in the trials 

themselves, but also have achieved the goal of improved quality of results within the forensic 

community as a whole.”130 

Results from the first large-scale, controlled experiment on the accuracy of fingerprint examiners 

appeared in 2011.131 Sacrificing the realism of casework for known ground truth, experimenters 

from the Noblis Corporation and the FBI presented latent print examiners with pairs of prints 

consisting of one latent print and one exemplar, each from known sources. Some of the pairs 

(520) were mates that came from the same finger. The rest (224) were nonmates that came from 

different fingers. These nonmated pairs were designed to yield difficult comparisons. Unusually 

similar exemplars in the nonmates came from searches of the prints of the 58 million persons 

then in FBI’s Integrated AFIS database. Moreover, an abnormally large proportion of the latent 

prints were of poor quality. 

 

126 509 U.S. 594 (1993). 127 Rand, Schürenkamp, and Brinkman, 2002, op. cit. 128 Ibid. 129 Rand, S., M. Schürenkamp, and B. Brinkmann. “The GEDNAP (German DNA Profiling Group) Blind Trial 

Concept Part II: Trends and Developments.” International Journal of Legal Medicine, 118, no.2 (2004): 83. 130 Ibid., p. 88. 131 Ulery, B., A. Hicklin, J. Buscaglia, et al. “Accuracy and Reliability of Forensic Latent Fingerprint Decisions.” 

Proceedings of the NAS. 2011.
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After a double-blind presentation of the mated and nonmated pairs to the latent print examiners, 

the experimenters measured the proportions of identifications132 for the mates (sensitivity) and 

nonmates (false positives), as well as the proportions of exclusions for the nonmates (specificity) 

and mates (false negatives). For the particular mix of mates and nonmates in the test set, they 

also determined the proportion of correct judgments among the identifications (positive 

predictive value) and exclusions (negative predictive value). Box 2.4 provides a small part of the 

data obtained and the resulting statistics on errors and accuracy. 

Of course, the experimental results may not lead to reasonable estimates of the rates at which 

errors occur in practice. To the extent that the experimental conditions and the examiners who 

are tested in the experiment do not mirror the conditions and examiners encountered in actual 

casework, the measured error probabilities will not apply directly to the field as a whole. They 

may, however, answer such questions as “How well do skilled examiners, working under ideal 

conditions on a difficult case, perform?” As noted, the legal system values the answers to such 

questions. Chapter 6 considers the admissibility of various statistics on error rates and offers 

recommendations on how an expert witness might approach the issue of error in a particular 

case.

Box 2.4: Selected Results of the Noblis-FBI Experiment

This experiment presented 169 relatively experienced and proficient latent fingerprint 

examiners, who knew they were being tested, with pairs of latent and exemplar prints selected to 

be challenging and judged by the examiners in the study to be representative of casework. The 

examiners worked through a total of 17,121 presentations of 744 image pairs (roughly 100 pairs 

per examiner). Table 2.8 summarizes the results of the examiners’ efforts for those pairs of 

prints that they initially deemed “of value for individualization.”133

Nonmate Mate All

Exclusion 3,622 450 4,072

Identification 6 3,663 3,669

Inconclusive 455 1,856 2,311

All 4,083 5,969 10,052

Table 2.8: Outcomes for pairs judged to be “of value for individualization” 

Of the presentations deemed of value for individualization (59%, or 10,052), five examiners 

(5/169 = 3%) made false identifications. One of the five examiners made two false 

identifications. Looking just to the outcomes likely to be seen in court—the identifications and 

exclusions—the false positive rate is 6/3,628 = 0.2%.134

 

132 During the study, examiners were asked to provide one of four decisions: “the analysis decision of no value 

(unsuitable for comparison); or the comparison/evaluation decisions of individualizations (from the same source), 

exclusion (from different sources), or inconclusive.” Ibid.

(For brevity, the discussion here is 

133 There were an additional 3,122 comparisons based on latent fingerprints deemed of value only for exclusion. 

Because standard operating procedures typically include only value-for-individualization comparisons, these other 

outcomes are not presented here.

134 In no case did two examiners make the same false positive error. The errors occurred on image pairs where a 

large majority of examiners made correct exclusions; one occurred on a pair where the majority of examiners judged 

the comparisons to be inconclusive. Thus, the six erroneous identifications probably would have been detected if an 

independent, blind verification were performed as part of the operational examination process.
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confined to this set of cases in which the examiners were able to make an identification or an 

exclusion.135)

As discussed earlier, “sensitivity” is the proportion of cases in which an examiner confronted 

with a mated pair makes a positive identification. Thus, in this experiment, the sensitivity was 

3,663/4,113 = 89.1%.136

Whereas the false positive rate was only 0.2%, the false negative rate was 450/4,113 = 10.9%.137

Defining specificity as the proportion of exclusions for nonmates judged to be of value for 

inclusion, the specificity was 3,622/3,628 = 99.8%.138 Table 2.9 summarizes these error and 

accuracy rates. 

Nonmate Mate

Exclusion Specificity: 99.8% False negative rate: 10.9%

Identification False positive rate: 0.2% Sensitivity: 89.1%

Table 2.9: Accuracy and error rates for exclusions and identifications in pairs judged to be 

“of value for individualization” and leading to exclusions or identifications

2.5 Summary

This chapter discussed types of error and the differences between process errors and outcome 

errors. It also reviewed how the system in which the examiner works can contribute to such 

errors. Finally, the chapter outlined the challenges and benefits of trying to calculate the 

prevalence of error in latent print examinations. 

 

135 Adding inconclusives lowers the false positive rate to 6/4,083 = 0.1%.

136 Again, the text deals only with the pairs deemed of value for identification and resulting in a definitive 

conclusion. The sensitivity was 3,663/5,969 = 61.4%, including inconclusives.

137 Adding inconclusives lowers the false negative rate to 450/5,969 = 7.5%.

138 Adding inconclusives lowers the specificity to 3,622/4,083 = 88.7%.
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Chapter 3: Interpreting Latent Prints

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Chapter 3: Interpreting Latent Prints

Introduction and Scope

Latent print examination requires the careful interpretation and comparison of friction ridge 

impressions. From the first examination of the features contained in a latent print to a final 

conclusion regarding an identification or exclusion, an examiner engages in many acts of 

interpretation. Current methods of interpretation are based upon professional knowledge and 

experience rather than formal decision thresholds or statistical models. 

This chapter describes the critical interpretative stages that are part of every latent print 

comparison. It surveys the current state of knowledge, based upon published research, regarding 

the interpretive stages and the implications for pitfalls that may arise during the interpretive 

process. It also identifies the most important questions in this area that require further study. 

Finally, this chapter provides recommendations and best practices relating to the interpretive 

stages. 

3.1 Preliminary Observations and Caveats

Several preliminary observations are important. To begin with, the chapter focuses almost 

exclusively on latent fingerprint examinations using the ACE-V process (Analysis, Comparison, 

Evaluation, and Verification), drawing on the Latent Print Examination Process Map of Chapter 

1 (Figure 1.1). This chapter maps the interpretive stages onto the relevant sections of that Process 

Map. The focus on ACE-V is not intended as an endorsement of ACE-V as a “methodology.” As 

explained in Chapter 1, ACE-V maps the steps of a process, but it does not provide specific 

functional guidance on how to implement that process, nor does it detail the substantive content 

of the various steps.139 Although ACE-V provides a useful framework for describing the steps 

taken for interpreting prints, it does not offer specific criteria to guide those interpretations. 

A second preliminary observation concerns the analysis of the subjective elements in human 

interpretation. To recognize such subjectivity is not to disparage the process. The act of 

interpreting inevitably requires human judgment and necessarily implies at least some 

subjectivity. If one simply follows a clear, bright-line rule with no discretion or independent 

judgment, one is not actually interpreting. Interpretation goes beyond merely executing a set of 

rules; thus, the exercise of judgment and expertise inevitably makes the interpretive process 

partly subjective. 

Third, with the subjectivity of interpretation comes the possibility of reduced performance 

because of human factors issues. As explained in Chapter 1, cognitive bias is one aspect of 

human interpretation that has received significant attention. Writing about sorting fingerprints 

according to Purkenje’s standards, Francis Galton recognized the difficulty of accurate 

interpretations of fingerprints and the possible dangers of cognitive bias: 

 

139 See also Mnookin, J. “The Courts, the NAS, and the Future of Forensic Science.” Brooklyn Law Review, 75, no. 

4 (2010): 1209.
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On considering the causes of these doubts and blunders, different influences were 

found to produce them, any one of which was sufficient by itself to give rise to 

serious uncertainty. A complex pattern is capable of suggesting various readings, 

as the figuring on a wallpaper may suggest a variety of forms and faces to those 

who have such fancies.140

All human interpretation is potentially subject to biasing effects, as the enormous research 

literature across a wide variety of domains establishes (as noted in Chapter 2). To recognize that 

latent print examiners are potentially subject to bias is not to single them out but rather to suggest 

that they are not exempt from those cognitive biases that all interpreters of data and information 

face. Indeed, many psychologists claim that susceptibility to bias is part of the architecture of the 

human brain. The same processes that help us make sound judgments in many circumstances 

also create the possibility for bias. In some instances, cognitive biases lead to improved 

performance, whereas in other circumstances they degrade performance.141 

Bias is only one of the many factors that can affect examiner performance. It receives particular 

attention in this chapter because of the extensive research on cognitive bias in other fields and 

the emerging research in this field that reveals the possible effects of bias on interpretive 

performance. Other chapters focus on other factors—from lighting, to technology access, to 

work culture—that also affect interpretation. Recognizing that a variety of human factors affect 

the interpretive process, this chapter examines the process with an eye toward identifying the 

facets that raise research and operational issues because of the possibility of cognitive bias. 

Fourth, although this chapter attempts to highlight those locations within the interpretive process 

of latent print examination where subjectivity and error due to human factors might be especially 

salient, it makes no effort to quantify the potential risk of error in latent print interpretation. The 

discussion is primarily theoretical. For the most part, the empirical basis for clearly establishing 

the extent of these risks does not yet exist. Further research is needed to establish whether, in 

what circumstances, and to what extent these theoretical issues of interpretation create an 

elevated risk for error. 

Many of the interpretive issues discussed in this chapter are well known to latent print 

examiners. However, some of the interpretive inflection points in the latent print identification 

process traditionally have not had precise names associated with them and are not clearly 

articulated in day-to-day practice. Enormous variability exists in how various forensic service 

providers approach these interpretive issues. This chapter offers a framework for thinking about 

interpretation, and it presents a vocabulary for considering the interpretive inflection points, but 

it does not attempt to detail the variations in approaches to interpretive questions across 

laboratories or jurisdictions. The major interpretive stages involved in latent print examination 

discussed in this chapter are as follows: 

• Feature selection: The examiner selects specific friction ridge details within a latent print 

on which to focus subsequent inquiry. 

 

140 Galton, F. Finger Prints. 1892. Reprint, William S. Hein & Co., 2003, p. 66. 141 Potchen, E., J. Gard, P. Lazar, et al. “The Effect of Clinical History Data on Chest Film Interpretation: Direction 

or Distraction?” Investigative Radiology, 14 (1979): 404.
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• Utility assessment: At various points in the latent print identification process, an 

examiner decides whether the print is of value for numerous purposes. Examples include 

assessing whether the latent is suitable for comparison, whether it is suitable for an 

automated fingerprint identification system (AFIS) search, and whether the potential 

source print is suitable for comparison. Because these interpretive determinations are all 

forms of sufficiency analysis, they are considered under a common rubric. 

• Feature weighting: An examiner assigns weight and significance to individual features 

and their configuration and assesses the overall strength of their synthesis. 

• Discrepancy interpretation: An examiner interprets the significance of observed 

divergences between a latent print and an exemplar and determines whether the 

differences establish that the two impressions arose from different sources or are 

consistent with a common origin.

• Source attribution: An examiner decides whether two prints share a common source, or 

determines that the information presented does not permit a categorical conclusion.142

In addition to discussing these interpretive stages individually, this chapter addresses a number 

of issues common to several interpretative stages, including the need to establish adequate 

documentation and the desirability of procedures to help avoid bias. The next section discusses 

these crosscutting issues and presents recommendations regarding them. The remainder of the 

chapter (1) describes the interpretive stages and explicitly connects them to the Latent Print 

Examination Process Map set out in Chapter 1, (2) describes and discusses any key published 

research findings that relate to the particular interpretive stage, (3) provides recommendations 

and best practices relating to the interpretive stage, and (4) highlights important research 

questions connected to each interpretive stage. 

3.2 Issues Relevant to Multiple Interpretative Stages 

3.2.1 Documentation 

One crosscutting issue is the need for adequate documentation of an examiner’s reasoning and 

conclusions. Documentation is not itself an interpretive practice, but rather a practice for 

capturing an examiner’s interpretive judgments in a form that would permit the examiner, or 

another examiner, to make sense of a decision at a later time. Documentation serves to maximize 

the transparency of the interpretative process and to provide a record that can be useful for many 

purposes, including reports and testimony, future research and evaluation, and quality assurance. 

Documentation requirements also may affect the interpretive process itself by requiring 

judgments to be explicit and thus potentially subject to greater reflection on the part of the 

examiner. 

 

142 There are other interpretive stages beyond the five described here. For example, it can be argued that a major step 

is classifying an impression as emanating from a finger or palm and determining what orientation to use to search 

the latent print. These decisions, if incorrect, can lead to a missed opportunity for an identification or to an erroneous 

exclusion. However, the focus here is on the steps that can present some of the more complex issues in 

comprehending the associated human factors concerns.
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Questions regarding how much documentation should be required clearly are relevant to feature 

selection, utility assessment, and discrepancy interpretation. How much documentation to 

provide is difficult to legislate because the degree and detail of documentation can vary 

depending on the complexity of the comparison. The more complex the cognitive and 

interpretive assessment, the more there is to be gained from detailed and explicit documentation. 

However, assessing the complexity of a comparison requires additional research. Without clear 

guidelines on complexity, the examiner’s subjective assessment of complexity can be used, but 

this assessment too should be part of the record. For both legal and scientific purposes (see 

Chapter 5), the documentation should supply detail sufficient for another expert to understand 

the basis for the examiner’s conclusions and to replicate the steps the examiner followed. 

Such documentation should be contemporaneous with the analysis or as nearly so as is 

practicable.143 Because the purpose of documentation is to capture an examiner’s interpretive 

process, both to assist that examiner in recalling what occurred and to make these processes as 

transparent as possible to others, documentation will be most helpful and accurate when 

conducted at the same time as the interpretation itself.144 The closer in time the documentation is 

conducted to the mental processes it details, the more complete and accurate the documentation 

is likely to be. 

Recommendation 3.1: A report and contemporaneous supporting notes or materials 

should document the examination to make the interpretive process as transparent as 

possible. Although the degree of detail may vary depending on the perceived complexity 

of the comparison, documentation should, at a minimum, be sufficient to permit 

another examiner to assess the accuracy and validity of the initial examiner’s 

assessment of the evidence. 

Another question that arises in more than one interpretative stage is the extent to which it is 

legitimate to reassess a latent print or other exemplar after looking at a potential source print. 

Norms and laboratory practices vary in this regard. At one extreme, some forensic service 

providers permit examiners to undertake comparisons without any prior explicit feature 

assessment in the questioned print. At another extreme, some providers discourage any “new” 

features from being noted in the latent print after comparison has begun. Anecdotal evidence 

suggests that many laboratories routinely reassess the features within the latent print after 

undertaking a comparison to a known exemplar. This recursive practice should not be ruled out, 

because the exemplar may draw attention to a genuine feature in the latent print that was not 

previously observed or that was interpreted as likely to be an artifact until the same feature was 

apparent in the comparison print. 145

However, recursion raises the possibility that an examiner will be unduly influenced by the 

exemplar when reassessing the latent print. In other words, although the comparison process may 

reveal true similarities regarding features that had not previously been noted, it also can lead to 

 

143 See American Society of Crime Laboratory Directors/Laboratory Accreditation Board. ASCLD/LAB Guiding 

Principles of Professional Responsibility for Crime Laboratories and Forensic Scientists. Principle 15, Version 1.1. 144 See U.S. Department of Justice, Office of the Inspector General. The FBI DNA Laboratory: A Review of Protocol 

and Practice Vulnerabilities. U.S. Department of Justice, May 2004. 145 Vanderkolk, J. Forensic Comparative Science: Qualitative Quantitative Source Determination of Unique 

Impressions, Images, and Objects. Academic Press, 2009, p. 23, 92 – 94.
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the perception of a similarity that does not exist. In some instances, the comparison print may 

help the examiner accurately clarify ambiguous minutiae in the latent image, whereas in other 

instances, an examiner may, in all good faith, be misled by what cognitive psychologists call 

expectation effects. Given this complex interaction between the interpretation of a latent and 

known print, this report can offer no hard rules about the appropriateness of making use of this 

interpretive practice. However, procedural steps can make the use of this interpretive procedure 

more transparent and reflective. At a minimum, there should be an explicit determination of 

features in the latent before the comparison process. This initial determination need not limit the 

features that can be used in subsequent analysis; identifying this initial set ensures that the 

analyst’s approach remains transparent. But because of the danger of bias emerging in going 

back and forth between latent and exemplar prints—and to maintain the transparency of the 

process—any features that are noted after comparison has begun or as the result of the 

comparison process (rather than before comparison begins) should be indicated and explicitly 

included in the documentation. 

Recommendation 3.2: Modifications to the results of any stage of latent print analysis 

(e.g., feature selection, utility assessment, discrepancy interpretation) after seeing a 

known exemplar should be viewed with caution. Such modifications should be 

specifically documented as having occurred after comparison had begun. 

3.2.2 Cognitive Biases 

Another crosscutting issue is cognitive bias. Chapter 1 notes the substantial body of 

psychological research illustrating the tendency for human beings to engage in motivated 

reasoning or to be affected by contextual knowledge. Even people attempting to be fair 

interpreters of the evidence may be influenced by information outside the formally relevant 

decision criteria. Such biases may be present in the work of latent print examiners.146 However, 

the extent to which cognitive bias creates the danger of erroneous interpretations in real-world 

circumstances has not yet received significant research attention. Continued research about the 

presence or absence of such biases in the latent print domain and the extent of any impact on 

accuracy and reliability is needed. However, given the decades-long research into the significant 

effects of cognitive bias in other domains, it seems wise to minimize the potential for such biases 

in latent print interpretation, even in the absence of definitive research results for latent print 

analysis. 

An obvious way to minimize the effect of contextual information is to keep the interpreter from 

having access to that contextual information in the first place. For example, the double-blind 

study is the gold standard for clinical drug testing because it ensures that the clinicians 

administering a drug and evaluating the patient’s response do not know whether the patient is 

receiving the drug or the placebo. Treating physicians still have all the information they need to 

provide quality care, but those participating in the testing process are shielded from the 

information that could bias them. 

 

146 Dror, I., D. Charlton, and A. Peron. “Contextual Information Renders Experts Vulnerable to Making Erroneous 

Identifications.” Forensic Science International, 156, no. 1 (2006): 74–78. See also authorities cited, Chapter 2.
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Currently, there is no systematic effort to blind forensic examiners from contextual information 

that is clearly not domain relevant—information that is not related to or necessary for their 

analysis. For example, the suspect’s prior convictions, gang membership, or confession does not 

assist in the print analysis. Such extraneous information could create bias. It is therefore good 

practice to avoid disclosing extraneous, domain-irrelevant information.147 To be sure, some 

information may be necessary at a later point in the forensic analysis and should be provided at 

that point. The goal here is not to define what information is necessary at each point in the 

analysis but simply to suggest that procedures should be designed to eliminate access to 

potentially biasing, domain-irrelevant information. 

Recommendation 3.3: Procedures should be implemented to protect examiners from 

exposure to extraneous (domain-irrelevant) information in a case. 

This recommendation is not suggesting that examiners should be denied access to information 

that is legitimately relevant to their substantive analysis. Examiners must have the information 

that is necessary to do their jobs effectively. Some information will be both potentially biasing 

and domain relevant—for example, information about the substrate from which a print was 

lifted, or the fact that the source print is the result of an AFIS search. Unless further research 

points to particularized dangers of bias, examiners should have access to whatever information is 

legitimately relevant to the exercise of their expertise, notwithstanding some theoretical but 

unproven danger of bias. 

However, given the genuine dangers of cognitive bias, the better practice is to protect examiners 

from inadvertent bias by shielding them from information that is clearly unnecessary and not 

relevant to their assessment. It might not always be feasible to implement such procedures, and it 

may well be infeasible to implement them perfectly. Forensic scientists strive to reach 

conclusions “based on the evidence and reference material relevant to the evidence, not on 

extraneous information, political pressure, or other outside influences.”148 If examiners routinely 

receive extraneous, domain-irrelevant information, forensic service providers should examine 

whether they can modify their procedures to shield examiners from this unnecessary and 

potentially biasing information. 

The three recommendations above apply to multiple interpretative stages. The sections that 

follow focus on the stages of the latent print analysis, with reference to the research that is 

relevant to each stage and recommendations (beyond those given above) that are specific to each 

stage of interpretation. 

3.3 Feature Selection

The first major interpretative stage in a latent print analysis occurs during the initial examination 

of the latent print. In this stage, the examiner identifies features in the latent print (e.g., ridge 

 

147 Others have made similar suggestions. E.g., Risinger, D., M. Saks, W. Thompson, et al. “The Daubert/Kumho

Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation and Suggestion.” California 

Law Review, 90, no. 1 (January 2002); Krane, D., S. Ford, J. Gilder, et al. “Sequential Unmasking: A Means of 

Minimizing Observer Effects in Forensic DNA Interpretation.” Journal of Forensic Sciences, 53, no. 4 (2008): 

1006–7. 148 ASCLD/LAB, Principle 2, op. cit.
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flow type or ridge path minutiae) that allow a determination of whether the latent print has 

sufficient detail to form the basis for subsequent comparisons. Section 3.5 provides figures and 

more explanation about minutiae and the levels of detail in print images.

3.3.1 Corresponding Phase in the Latent Print Examination Process Map

One of the primary tasks of the Analysis phase of the ACE-V process is the selection of reliable 

friction ridge features in a latent print for comparison against features in exemplar prints. This 

corresponds to steps 210 and 320 in the Latent Print Examination Process Map (Figure 1.1). The 

process of feature selection may occur simultaneously with the other interpretative processes 

such as analysis of distortion and suitability determination (see the discussion of these topics 

below and steps 210 through 240 in the Process Map). These interpretative processes, in fact, 

may all color and influence each other because they have direct impact on the determination of 

the quantity, quality, and reliability of the features selected for analysis.

3.3.2 Findings from Existing Research 

Feature selection begins with an analysis of the latent print by itself. This generally occurs—and 

should generally occur—before viewing the exemplar print. The features that will be selected 

usually include those that are the most clearly visible and distinctive, and they will serve as the 

basis for the comparison against exemplar prints. 

In studying a latent print, an examiner will likely note some minutiae that he is certain exist and 

other that he is less sure about. The former should be the primary focus. Confidence about a 

feature refers to two things: (1) the examiner is confident that the feature genuinely exists in the 

latent print, and (2) the examiner strongly expects to observe that feature in a corresponding 

exemplar print from the same source. The degree of expectation relates to the level of tolerance 

that the examiner is willing to accept when observing differences during the subsequent 

Comparison phase. In other words, if an examiner believes a feature exists in the latent print and 

strongly expects to see it in any print from the same source, then the absence of the feature could 

significantly affect the examiner’s source attribution. The effect of this feature’s absence 

increases with the examiner’s confidence that the feature existed in the original latent print (and 

could not be interpreted as anything else). 

Typically, high-confidence features will have the highest reliability (accuracy and precision in 

selection).149 Because these features will form the basis for the decision, the manner in which 

they are selected, how they are documented, and what level of confidence is assigned to them 

become critical in understanding the examiner’s decision-making process. Feature selection 

becomes crucial in the examination because criteria for the decision-making processes are 

neither clearly defined a priori nor made using an objective, validated metric. 

Defining the Features

Examiners are not limited to the “points” or “minutiae” when selecting features during the 

Analysis phase (although commonly these may be the only formal features documented). 

 

149 Langenburg, G. and C. Champod. “The GYRO System—A Recommended Approach to More Transparent 

Documentation.” Journal of Forensic Identification, 61, issue 4 (July/August 2011): 373 – 384.
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Examiners will utilize several classes of features, often referred to as “levels of detail.” There are 

also occasional features not associated with any of the traditional levels of detail that appear, 

such as creases and wrinkles, permanent scars, temporary skin damage, or skin disease, that 

examiners might use.150

Level 1 Detail (L1D) is defined as “ridge flow.”151 Ridge flow often translates to a pattern type 

in a finger or palm, such as a loop, whorl, or arch formation; ridge flow also includes other 

information such as relative curvature. Pattern types are class characteristics shared by many 

individuals. Furthermore, L1D can be easily distorted as a result of the flexibility of skin.152

Therefore, although L1D might be selected, this level of detail is not always reliable, especially 

if signs of distortion appear in the image. Figure 3.1 provides illustrations of some L1D. 

Level 2 Detail (L2D) is defined as “ridge path.”153 L2D includes minutiae, such as ridge endings, 

bifurcations, or dots. Even the absence of minutiae in an area (called an “open field”) can be 

significant and highly discriminating. Ridge path features are also some of the most robust 

features, and they will be present even under extreme conditions of distortion.154 They also tend 

to be highly discriminating155 and thus are ideal features for comparisons.

Level 3 Detail (L3D) refers to the edges of ridges (which may appear indented or protruded) and 

pores (the location of the center of the pore, not the size or shape, which can be highly variable 

within a source).156 Although the reproducibility of pores in latent prints (or low-resolution 

capture systems for exemplars) can be problematic in low-clarity images, these features can be 

highly discriminating when visible.157

 

150 This will vary significantly among jurisdictions. For example, in countries that require a minimum number of 

minutiae to declare an identification, scars and creases may not be used to reach the minimum. Other agencies may 

be unwilling to use creases to contribute to the identification decision but will use creases to narrow a search through 

set of exemplar prints.

151 Ashbaugh, D. Quantitative-Qualitative Friction Ridge Analysis: An Introduction to Basic and Advanced 

Ridgeology. CRC Press, 1999.

152 Maceo, A. “Qualitative Assessment of Skin Deformation: A Pilot Study.” Journal of Forensic Identification, 59, 

no. 4 (2009): 390–440.

153 Ashbaugh, op. cit. 154 Maceo, op. cit. 155 Egli, N., C. Champod, and P. Margot. “Evidence Evaluation in Fingerprint Comparison and Automated 

Fingerprint Identification Systems—Modelling Within Finger Variability.” Forensic Science International, 167 

(2007): 189–95; Jain, A., Y. Chen, and M. Demirkus. “Pores and Ridges: High-Resolution Fingerprint Matching 

Using Level 3 Features.” IEEE Transactions on Pattern Analysis and Machine Intelligence, 29, no. 1 (2007): 15–27; 

Neumann, C., C. Champod, R. Puch-Solis, et al. “Computation of Likelihood Ratios in Fingerprint Identification for 

Configurations of Any Number of Minutiae.” Journal of Forensic Sciences, 52, no. 1 (2007): 54–64; Srihari, S., H. 

Srinivasan, and G. Fang. “Discriminability of Fingerprints of Twins.” Journal of Forensic Identification, 58, no. 1 

(2008): 109–27.

156 Roddy, A. and J. Stosz. “Fingerprint Features—Statistical Analysis and System Performance Estimates.” 

Proceedings of the IEEE, 85, no. 9 (1997): 1390–1421; Richmond, S. Do Fingerprint Ridges and Characteristics 

Within Ridges Change with Pressure? Australian Federal Police, Forensic Services, 2004.

157 Jain, Chen, and Demirkus, op. cit.; Kryszczuk, K., A. Drygajlo, and P. Morier. “Extraction of Level 2 and Level 

3 Features for Fragmentary Fingerprint Comparison.” In Proceedings of the Second COST Action 275 Workshop, 

2004, 83–88.
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Occasional features such as scars and creases can be selected. These features vary in their 

reproducibility. For example, creases may not always reproduce consistently158 but can be fairly 

discriminating,159 whereas scars reproduce very consistently and are also believed to be highly 

discriminating.160 In some instances, such as temporary skin damage, there is a low expectation 

of reproducibility in exemplar prints, but the presence of such a feature can be highly significant. 

How examiners select and document features can vary significantly among jurisdictions. In some 

instances, the examiner observes and notes features to use for comparison without producing any 

formal documentation; this examiner might change his mind about the features selected without 

documenting the change. On the other end of the spectrum, some examiners formally select 

features a priori and annotate the features during the Analysis phase. In some agencies, 

examiners must justify in writing any modifications made to their initial feature selections during 

the Comparison phase. 161

Whether features are selected formally or informally, there are two major decision components 

involved: determining the existence of a feature and identifying the type or shape of the feature. 

These decisions are distinct, and each decision can have its own assigned level of confidence. In 

other words, deciding if a feature is present is different from determining precisely what the 

feature is. Both decisions may be limited by the quality and clarity of the image.

The determination that a feature exists is akin to the concept of signal-to-noise ratio 

determination. Typically, a targeted feature produces a stimulus signal to the observer greater 

than the background noise. In some instances, additional information near the suspected signal is 

relevant to ascertaining the existence of a feature. An example would be the observation that 

adjacent ridges next to a suspected feature react to account for the presence of the suspected 

feature. Another example would be three ridges entering a small smudged area from which only 

two ridges exit. These indicators allow an examiner to infer the existence of a feature that cannot 

be observed directly. 

The identification of the type of feature observed is, as a logical matter, a separate inquiry made 

after determining the existence of a feature. For this decision, the examiner will attempt to 

classify and identify the type of feature with as much specificity as possible. For example, after 

noting L1D that includes a recurve and a single delta formation, the examiner might classify this 

ridge flow as a loop pattern. Similarly, an examiner observing a ridge path event may conclude 

that the feature is an ending ridge or a bifurcation (illustrations of these minutiae are available in 

Table 3.4 and Figure 4.3). Or perhaps the examiner cannot tell and will simply refer to the 

minutiae as a “ridge event.” In this last scenario, the examiner has no doubt that a minutia exists 

in the latent print, but the examiner cannot, on the basis of what is observable in the latent image, 

 

158 Richmond, op. cit. 159 Tietze, S. and K. Witthuhn. Papillarleistenstruktur der menschlichen Handinnenfläche. Luchterhand, 2001.

160 Feng, J., A. Jain, and A. Ross. “Detecting Altered Fingerprints.” In 2010 20th International Conference on 

Pattern Recognition (ICPR), August 2010, 1622–25.

161 See, e.g., Interpol European Expert Group on Fingerprint Identification – IEEGFI II. Method for Fingerprint 

Identification. Interpol European Expert Group on Fingerprint Identification – IEEGFI II, 2004; U.S. Department of 

Justice, Office of the Inspector General. A Review of the FBI’s Handling of the Brandon Mayfield Case 

(Unclassified and Redacted). U.S. Department of Justice, March 2006.
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determine the specific type of minutia. The examiner, in this instance, has great certainty about 

the minutia’s existence, but great uncertainty about its specific nature. 

For each of these decisions—determining the existence of the feature and determining the type of 

feature—the examiner has some internal level of confidence. This level of confidence may be 

documented formally, or it may simply be an informal or even implicit judgment by the 

examiner, depending on local practices. The levels of confidence can also be very different for 

the two decisions. For example, the examiner might be highly confident that a feature exists 

when three ridges enter a smudged area but only two exit; yet the examiner might have no 

confidence regarding whether the event is a bifurcation or ridge ending (although the examiner 

might have high confidence about what the feature is not—for example, a dot). 

3.3.3 Issues and Recommendations

Confidence Levels and Documentation

During feature selection, there may be a wholly implicit or a more explicit assignment of weight 

to the features, mostly as a function of their specificity (discriminating strength). This chapter 

covers weighting of features in section 3.5; here the focus is on the role of an examiner’s 

confidence in such weighting and the importance of documenting the degree of confidence. An 

examiner’s confidence in the existence of the feature and confidence in its classification will 

undoubtedly affect the weight applied to the feature, independent of specificity. Generally 

speaking, examiners would give more weight to a rare feature, such as a trifurcation, when it is 

clear and distinct and when the examiner is confident in selecting it than when it is part of an 

indistinct, distorted, or low-quality area that may possibly include a trifurcation or something 

else (or may not even exist). Weight is a function of both confidence about the feature’s 

existence and the perceived rarity of the feature. Because not enough is known about rarity, and 

even that which is known is not necessarily part of an examiner’s formal training, this aspect of 

interpretation is often an implicit judgment based on the examiner’s experience.

162

The examiner’s decisions in the Analysis phase and the associated levels of confidence will only 

be captured by documenting these aspects contemporaneously. An examiner may choose to 

document the features and levels of confidence using a narrative, although this can be somewhat 

time-consuming and burdensome. Another way to record this information is to annotate the 

features with dots, tracings, and other markings on a photograph of the latent print. Numerous 

software packages can facilitate this process. Some software has been designed for fingerprint 

case annotation and includes tools for marking various friction ridge features, classifying these 

features, and assigning levels of confidence to the decisions.163 Newly developed algorithms, 

such as used in an automated quality mapping assessment,

164

 

162 Osterburg, J. “An Inquiry into the Nature of Proof. The Identity of Fingerprints.” Journal of Forensic Sciences, 9, 

no. 4 (1964): 413–27. Osterburg explored this issue and found large differences in examiners’ perceived 

contribution for different minutia types and their configurations. However, Osterburg’s study had significant 

limitations in its design and execution.

may be able to extract features 

automatically and to assign a level of confidence in the existence of the feature. While waiting 

163 Langenburg and Champod, 2011, op. cit. 164 See, e.g., Tabassi, E. and C. Wilson. “A Novel Approach to Fingerprint Image Quality.” IEEE International 

Conference on Image Processing, 2 (September 2005): 37–40; Nill, N. “IQF (Image Quality of Fingerprint) 

Software Application.” MITRE (May 2007). Accessed April 22, 2011. http://www.mitre.org/tech/mtf/.
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for this software to be further tested and more readily available, however, some examiners have 

developed annotation schemes for indicating their personal assessments of confidence in the 

existence of a feature. For example, one scheme uses colors to represent an examiner’s level of 

confidence.165 Similar to a traffic light, green features represent high confidence, yellow features 

represent medium confidence, red features represent low confidence, and orange features are 

those observed during the Comparison phase. This report does not offer specific prescriptions 

regarding which approaches or technologies should be used; however, tools that make explicit 

documentation both more routine and less time-consuming for examiners offer significant 

benefits to the interpretive process. 

If time were no limitation, elaborate, formal documentation of all discriminative features in 

advance of a comparison would be ideal. The examiner would document all relevant and 

significant features observed and would record the confidence regarding these features before 

engaging in comparison. This annotation in advance would make explicit whether any significant 

features were noted only after the comparison had begun, whether the examiner’s confidence in 

the existence of minutiae changed as a result of the comparison process, and whether these 

changes were justified. It would make the examiner’s internal thought process more transparent 

to later observers and more transparent to the examiner himself. 

However, not every comparison is complex, and time and resources are limited. Heavy caseloads 

are the norm for many forensic service providers. Therefore, the benefits of detailed and 

formalized documentation requirements must be balanced against the time and resources they 

require. Recommendation 3.1, regarding the importance of documentation to maintain 

transparency, which is highly relevant to feature selection, attempts to provide this balance by 

requiring some degree of contemporaneous documentation in all cases while also recognizing 

that the degree and detail of documentation may vary with the complexity of the print and the 

comparison. 

Variation

Intra-examiner reliability refers to reproducibility on the part of the same examiner. Intraexaminer reliability would be present during feature selection when an examiner selects certain

features in a questioned latent print at one time and selects different features from the same print 

at a later time (without recollection of the initial features selected). Inter-examiner

reproducibility refers to the variation that exists across different examiners—variation that 

occurs when different examiners are presented with the same latent print and independently 

select different features. Studies of intra-examiner and inter-examiner variation reveal significant 

differences.

166 Methods to reduce variation in feature selection are currently being explored and 

tested.167

 

165 Langenburg and Champod, 2011, op. cit.

In the meantime, because inter-examiner variation can be extensive, an examiner 

cannot assume that another examiner will see the same features (or place the same level of 

166 Evett, I. and R. Williams. “A Review of the Sixteen Points Fingerprint Standard in England and Wales.” 

Fingerprint Whorld, 82 (1995): 125–43; Langenburg, G. “Pilot Study: A Statistical Analysis of the ACE-V 

Methodology—Analysis Stage.” Journal of Forensic Identification, 54 (2004): 64–79; Dror, I., C. Champod, G. 

Langenburg, et al. “Cognitive Issues in Fingerprint Analysis: Inter- and Intra-Expert Consistency and the Effect of a 

‘Target’ Comparison.” Forensic Science International, 208 (2011): 10–17.

167 Langenburg, G., C. Champod, T. Genessay, et al. “Informing the Judgments of Fingerprint Analysts Using 

Quality Metric and Statistical Assessment Tools.” National Institute of Justice Impression and Pattern Evidence 

Symposium, Clearwater, Florida. August 2010.
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confidence in the existence of any given feature).168 Documentation of the feature selection 

process is critical to understanding the differences among examiners and their decisions. 

Examination Complexity 

Not all print comparison tasks are equal in difficulty. Some comparisons are simple; others are

far more complex. Although there is no formal method or metric for assessing complexity, 

experience and common sense point to some of the relevant factors. Examples of factors that 

lead to complexity include significant elements of distortion, reduced image quality (clarity), few 

reliable features available for comparison, or unusual, rare features to consider. 

As described in Recommendation 3.1, the amount of documentation needed may vary depending 

on the complexity of the particular examination. In fairly simple, unambiguous cases, examiners 

appear to be fairly resistant to certain bias effects.169 Furthermore, although extensive interexaminer variation in feature selection appears to exist, some research suggests that this variation 

does not have significant effects on the ultimate decisions in noncomplex cases, but it is more

significant in complex cases.

170 

These findings comport with intuition. When information is clear and plentiful, different 

examiners may elect to focus on different minutiae and yet reach consistent results. For the sake 

of efficiency, in these simple cases with significant quantity and quality of features present, 

minimal documentation may be sufficient because the risk of error due to bias or other human 

factors is also fairly minimal. Conversely, in complex cases, with limited quantity and quality of 

features, research shows that a variety of factors can influence interpretation and decisions.171 In 

these more difficult interpretations, documenting all available and reliable features and following 

stricter protocols regarding the analysis of the latent print before exposure to an exemplar can be 

critical in reducing the potential for error.

However, if documentation is permitted to vary with the complexity of the examination, 

examiners need to be able to determine complexity. It then becomes very important during the 

Analysis phase that the examiner both assesses and documents the complexity of the case. 

Current research is attempting to develop tools and metrics for quantitatively assessing the 

difficulty or complexity of a latent print comparison. In the meantime, an examiner’s subjective 

assessment of case complexity can, by necessity, substitute, but this judgment must be 

documented in the case record. Some agencies may elect to institute a quality assurance policy or 

minimum minutiae threshold to assist in deciding how to document a case. For example, a 

 

168 An illustration can be found in the responses of the dozens of examiners in the public judicial inquiry set up by 

Scottish Ministers to verify the fingerprints associated with the case of H.M Advocate v. McKie in 1999, and related 

matters. Many chartings of the disputed latent print Y7 were submitted into evidence. Experts in the case disagreed 

about which features were reliable. Transcripts and court exhibits can be viewed at 

www.thefingerprintinquiryscotland.org.uk, accessed June 2, 2011. 169 Dror, I., A. Peron, S. Hind, et al. “When Emotions Get the Better of Us: The Effect of Contextual Top-Down 

Processing on Matching Fingerprints.” Applied Cognitive Psychology, 19 (2005): 799–809; Dror, I. and D. Charlton. 

“Why Experts Make Errors.” Journal of Forensic Identification, 56, no. 4 (2006): 600–16.

170 Evett and Williams, op. cit.; Dror, Charlton, and Peron, op. cit.; Langenburg, G., C. Champod, and P. Wertheim. 

“Testing for Potential Contextual Bias Effects During the Verification Stage of the ACE-V Methodology When 

Conducting Fingerprint Comparisons.” Journal of Forensic Sciences, 54, no. 3 (May 2009): 571–82. 171 Stacey, R. “A Report on the Erroneous Fingerprint Individualization in the Madrid Train Bombing Case.” 

Journal of Forensic Identification, 54, no. 6 (2004): 706–18; Dror, Charlton, and Peron, op. cit.
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forensic service provider might require examiners to document all features during the Analysis 

phase when a latent print has fewer than 12 minutiae. 

Recursive Practice

Once the examiner enters the Comparison phase and compares the latent print against an 

exemplar print (beginning with step 500 on the Latent Print Examination Process Map), looking 

at the exemplar may cause the examiner to re-evaluate aspects of the latent print. The examiner 

might use features in the exemplar print to find new features or to reassess previously noted 

features in the latent print. This practice, which has been referred to as “teasing the points”172

when used to attain a required minimum number of minutiae, poses possible concerns about bias. 

Some have criticized it as a form of circular reasoning because it uses the exemplar to infer 

meaning from the source print and vice versa.173 However, there are occasions when the 

exemplar may legitimately draw clearer attention to an important feature or reveal that some 

detail in the latent print previously thought to be “noise” is actually “signal.” 

Some sources, describing the advantages of a more cyclical process, defend examinations that 

move back and forth between latent and exemplar prints,174 whereas other sources discourage it 

in favor of a more linear approach.175 The difficulty is that the comparison print may lead both to 

accurate and inaccurate judgments about previously unnoticed features of the latent print, and 

there is no foolproof way to tell the two apart. Eliminating recursion would protect against 

picking or trimming the data to fit the conclusion, but it would also prevent the examiner from 

using valuable information. Moreover, recursive examinations may be especially important for 

reaching the conclusion to exclude. If the examiner sees several similarities between a latent and 

exemplar, notices another feature in the potential source print, returns to the latent, and does not 

see the corresponding feature, then the examiner is engaging in a form of recursion; yet even 

those who criticize recursive examinations would likely not wish to prevent such an analysis. 

Recently, Dror et al.176 and Langenburg et al.177

 

172 Evett and Williams, op. cit.; Tiller, C. “Fingerprint Identification in the United Kingdom—Do They Really Need 

16 Points?” Canadian Identification Society Newsletter, 39 (1983): 11.

 proposed using features in the latent print that 

were selected after observing the exemplar only if the nonlinearity of the process is documented. 

These sources recommend that if these features are used, they must be formally documented as 

features observed during, rather than prior to, the Comparison phase, and typically they should 

be assigned less weight than if the feature had been observed initially in the Analysis phase. This 

documentation-focused compromise has significant merit. This approach is captured in 

Recommendation 3.2, which states that any modification to an analysis after examining the 

exemplar (both in feature selection and in other interpretive phases) should be formally 

documented. 

173 IEEGFI II, op. cit.; U.S. Department of Justice, Office of the Inspector General, op. cit., p. 138. 174 Vanderkolk, 2009, op. cit.; Triplett, M. and L. Cooney. “The Etiology of ACE-V and Its Proper Use: An 

Exploration of the Relationship Between ACE-V and the Scientific Method of Hypothesis Testing.” Journal of 

Forensic Identification, 56, no. 3 (2006): 345–55.

175 Haber, L. and R. Haber. Challenges to Fingerprints: A Guidebook for Prosecution and Defense and Examiners. 

Lawyers and Judges Publishing Co., 2009; IEEGFI II, op. cit. 176 Dror, Champod, Langenburg, et al., op. cit.

177 Langenburg and Champod, 2011, op. cit.
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Cognitive Bias 

Various studies have shown that context information or other external factors can influence 

feature selection.178 However, some of this research has shown that not all bias effects are 

necessarily negative. At times, the biases can create more conservative decisions by examiners, 

even during feature selection. Whether greater conservatism is a plus or a minus depends on 

factors not yet fully understood (such as error rates in a variety of circumstances as well as 

policy decisions regarding tradeoffs between Type 1 and Type 2 errors). More study of the 

risks—and any benefits—of these bias effects and how to minimize them is warranted. One 

advisable countermeasure for bias in feature selection is simply to select features in the latent 

print separately from the exemplar. More generally, sequential unmasking, which excludes

irrelevant contextual information, is a valuable strategy. 

3.3.4 Research Needs in Feature Selection

Assessing Variation in Feature Selection

A handful of studies have assessed variation in the feature selection process. Generally, they find

a wide variation among examiners during the task of feature selection. At this stage, what may be 

of more interest to the community are methods to reduce the variation of feature selection and 

tools and technologies to help identify the most reliable features. These tools are likely to be 

especially important for complex comparisons, and they may have benefits more broadly. 

Link between Feature Selection and Source Attribution

The link between variations in feature selection and the examiner’s ultimate decision is not well 

understood. Emerging research suggests that there is a relationship,179 but the effect may be 

competing with other major interpretative steps, such as interpreting discrepancy, feature 

weighting, and thresholds for reaching identification decisions. A better understanding of the link 

between feature selection and the ultimate decision would permit best practices to be formulated 

and would allow technology to select the most reliable and useful features on which to base 

decisions later in the ACE-V process. 

What is clear from the research is that in complex cases, examiners who perceive and compare a 

greater number of features are more likely to reach a conclusion about source attribution (rather 

than determining the print to be inconclusive). Therefore, in complex cases, there is a strong 

need for tools or methods to standardize the selection of features. More generally, standardized 

methods for feature selection should result in less variation in the features that are selected and 

compared, which in turn should lead to more consistency in the decisions. However, even if 

decisions were more consistent, they would not necessarily be more accurate. It is possible, for 

example, that the best interpreters of prints would be more accurate using their own methods 

instead of following a standard protocol. This too, deserves attention and research. 

 

178 Evett and Williams, op. cit.; Dror, Charlton, and Peron, op. cit.; Langenburg, Champod, and Wertheim, op. cit.; 

Dror, Champod, Langenburg, et al., op. cit.

179 Langenburg, Champod, Genessay, et al., op. cit. 
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3.4 Utility Assessment

Several points in the latent print analysis process require a determination of latent print utility or 

sufficiency. The examiner must determine whether the print has enough clarity and quantity of 

information for some specified purpose. This happens both early in the process (e.g., 

determinations of whether the latent is suitable for analysis or suitable for an AFIS search) and 

later in the process (e.g., determinations of sufficient information to compare the latent and 

exemplar). For convenience, the common points are discussed here, since the recurring question 

is whether there is sufficient information for making the next inquiry. 

3.4.1 Corresponding Steps in the Latent Print Examination Process Map

Key points at which utility determinations are relevant are discussed here with the numbers in 

parentheses referring to steps in the Latent Print Examination Process Map. Upon acquiring a 

latent print, an examiner must determine whether it is suitable for comparison (step 240). This 

typically involves examining the details and any relevant distortion in the latent print to 

determine whether there is enough usable information to make a comparison viable. Assuming 

the latent print is suitable and that known prints are available, the examiner next determines if 

the known prints are suitable for comparison (step 350) and if the two prints combined are 

sufficient to see the comparison through to a decision (step 370). If no known prints are 

available, the examiner may be called on to determine if the latent print is suitable for an AFIS 

search (step 270). 

3.4.2 Findings from Existing Research

The Working Group found no research that effectively addresses utility or sufficiency in the 

context of fingerprint analysis. This is unsurprising, for a critical piece for any such research—

the definition and validation of a metric for assessing utility—is still missing. Research has been 

carried out related to the examiner decision process that implicitly involves judgments of utility 

and sufficiency, but these studies tend to focus only on the accuracy or repeatability of the 

ultimate decision and thus are reviewed in the relevant sections below. 

3.4.3 Recommendations and Best Practices

The absence of research findings specific to the determination of utility precludes evidencebased recommendations to guide practitioners. Instead, the primary findings with regard to utility 

determination concern practices to encourage consistent decision-making and to allow for 

ongoing evaluation of quality both within and across forensic service providers. This involves 

Recommendation 3.1, regarding the importance of documentation, and Recommendation 3.2, 

regarding the special importance of documenting any utility determinations that are altered after 

examining the exemplar. Such documentation is critical in utility determinations because it 

allows for internal quality control and quality assurance. It also is of great importance for any 

potential future external evaluations of quality. 

Agencies and forensic service providers can enhance the transparency of their analyses and 

conclusions by determining clear guidelines that assist examiners in making determinations of 

utility. This refers to guidelines for deciding whether a print warrants further assessment and not
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to guidelines for making ultimate source attribution. For example, an agency might require at 

least five minutiae to conduct an AFIS search. 

This chapter does not propose particular guidelines for determining utility but suggests that each 

forensic service provider try to make this step as explicit as possible. Until a substantial research 

basis exists from which best practices can be generated, it is inappropriate to require field-wide 

shared standards. Nevertheless, forensic service providers can draw on experience to establish 

clear guidelines. Information that could be incorporated in an agency’s guidelines includes 

number of minutiae and visibility of ridge flow, pores, ridge edges, and details of incipient 

ridges, creases, and scars. The guidelines for determining whether a latent print is suitable for 

comparison are necessarily different from the guidelines for comparing a pair of prints. 

Recommendation 3.4: Each agency or forensic service provider should define “suitable” 

or “sufficient” in its standard operations procedures. These guidelines should be as 

explicit as possible about what is expected for sufficiency determinations at different 

stages of the latent print examination process. 

The Working Group takes no position on whether agencies should couch guidelines as 

recommendations or as requirements. 

3.4.4 Research Needs in Utility Assessment

Existing research has not resolved the questions of utility, sufficiency, and value determination 

in latent print analysis. The Working Group strongly endorses further research in this area to 

enable the development of evidence-based guidelines and recommendations for utility 

determination. Although a general discussion of the need for research and a recommendation 

regarding research is provided near the end of the chapter, some preliminary thoughts regarding 

research questions relevant to utility or value determinations are provided here. 

Important areas for study include the following: 

• Reproducibility and accuracy: It is of great interest to understand the degree to which 

utility determinations are reliable. For each utility determination, researchers could 

present the same print at different times to a single examiner, present the same print to 

different examiners, or both. These studies could provide significant information about 

consistency, though they would not tell the researcher anything directly about accuracy. 

Assessing the accuracy of utility determinations is more problematic because there is no 

objective basis for ascertaining when a determination is correct. 

• Factors affecting utility determinations: A wide range of factors can affect utility 

determinations. One possible topic for consideration is context effects: does the type of 

case (e.g., violent crime versus property crime) have an effect on the determination of 

utility, or does background knowledge about the case affect utility judgments? Another 

possible topic is comparator effects: are different utility determinations obtained for 

comparing latent prints with suspect prints as opposed to comparing latent prints with 

AFIS-generated targets? Other factors that should be studied include forensic service 

provider culture norms and other human factors. 
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• The effect of laboratory culture: The relationship between the culture and expectations in 

an agency and examiner performance has not been studied. For example, do laboratories 

that frown on inconclusive determinations eliminate more prints at an earlier utility 

stage? 

• Utility effects with relation to manual, as opposed to AFIS, search strategies: Research 

could investigate, for example, whether certain pattern types create different utility 

strategies in relation to searching manually or on AFIS.

3.5 Feature Weighting

Practitioners recognize that assigning weights to latent print features and their configuration is a 

fundamental decision-making or interpretive step, either as an output of the Analysis phase or as 

part of the Evaluation phase. Pioneers such as Locard indicated that fingerprint features should 

be assessed as a function of their relative rarity (and clarity). 180

3.5.1 Frequencies of Friction Ridge Details

As discussed in section 3.1, the weighting of individual features currently reflects subjective, 

experience-based judgments of the probability associated with their occurrence. Whether done 

subjectively or in a more data-oriented fashion, weighting is a probabilistic assignment of the 

selectivity of the features being considered. The process of weighting among practitioners today, 

however, remains essentially holistic, and the subjective probabilities are rarely made explicit.181

In addition, no clear consensus exists among practitioners as to the reproducibility and perceived 

contribution of L3D features appearing in both latent and exemplar prints.182

Although individual experience may provide some insight into probabilities, carefully collected 

data should be used to provide more accurate assessments that can inform the weighting of 

features in the interpretive process. To demonstrate the nature and value of such data, this section

summarizes the major sources of data available on the classification and prevalence of L1D 

features (general flow of the ridges) and L2D features (here restricted to minutiae) for 

fingerprints.183 Limited statistical data are available for L3D features of fingerprints. Other types 

of friction ridge impressions (palms, toes, etc.) do not yet have comparable data available for 

even L1D features. 

L1D Features 

The prevalence of different types of L1D features in the population is well documented. 

Dermatoglyphic data from studies in anthropology, population genetics, and early detection of 

 

180 Locard, E. “La Preuve Judiciaire par les Empreintes Digitales.” Archives d'Anthropologie Criminelle, de 

Médecine Légale et de Psychologie Normale et Pathologique, 29 (1914): 321–48.

181 In fact, in one early study, latent print examiners did not provide consistent rankings of how frequently 

fingerprint features occur. Osterburg, op. cit. 182 Anthonioz, A., N. Egli, C. Champod, et al. “Level 3 Details and Their Role in Fingerprint Identification: A 

Survey Among Practitioners.” Journal of Forensic Identification, 58, no. 5 (2008): 562–89.

183 Part of this section is based upon a report of C. Champod, provided on September 28, 2009, to the Scottish 

Ministers’ Fingerprint Inquiry, available at www.thefingerprintinquiryscotland.org.uk/inquiry/2090.html, accessed 

April 22, 2011.
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disease, are one source.184 These data can be used in forensic science, but the classifications 

often do not match those used by forensic experts. Other data come from collections of ten-print 

cards. The majority of large collections were classified according to the Galton-Henry scheme,185

as illustrated in Figure 3.1: 

Arches Tented Arches Right Loops Left Loops

Plain Whorls Central Pocket 

Loops Double Loops Accidental Whorls 

Figure 3.1: Level 1 Detail features186

 

184 See, e.g., Kumbnani, H. “Dermatoglyphics: A Review.” In Anthropology Today: Trends, Scope and Applications, 

edited by M. Bhasin and V. Bhasin, 285–95. Kamla-Raj Enterprises, 2007. 185 Henry, E. Classification and Uses of Finger Prints. 4th ed. George Routledge and Sons, 1900. 186 Images adapted from Royal Canadian Mounted Police. Fingerprint Manual. Chapter 2. Royal Canadian Mounted 

Police, 1990.
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Data from the Federal Bureau of Investigation’s National Crime Information Center permits 

estimates of the prevalence of each class of L1D in the U.S. population. 

0.09%

Male Left Hand Patterns Male Right Hand Patterns

Arches 3.6% 2.9%

Tented Arches 3.1% 2.7%

Right Loops 3.9% 58.0%

Left Loops 63.7% 4.4%

Plain Whorls 17.3% 24.4%

Central Pocket Loops 3.8% 4.1%

Double Loops 4.1% 3.2%

Accidental Whorls 0.1% 0.083%

Missing or Amputated 0.2% 0.2%

Scarred or Mutilated 0.094%

Table 3.1: Distribution for the general patterns on fingerprints from the left and right hands of males 

(89,755,960 fingers)187

The relative frequencies of L1D can vary depending on the finger considered and, to some 

degree, the sex and ethnic background of the population. For example, comparing right thumbs 

to the little fingers of males produces the distributions in Table 3.2. 

Male Right Thumb Patterns Male Right Little Finger Patterns

Arches 2.5% 0.7%

Tented Arches 0.4% 0.6%

Right Loops 50.8% 82.3%

Left Loops 0.4% 0.3%

Plain Whorls 34.8% 11.8%

Central Pocket Loops 1.1% 3.6%

Double Loops 9.9% 0.4%

Accidental Whorls 0.021% 0.009%

Missing or Amputated 0.088% 0.1%

Scarred or Mutilated 0.025% 0.059%

Table 3.2: Distribution for the general patterns on fingerprints from the right thumb and little fingers 

of males (17,951,192 fingers)188

Some classes of L1D can be subdivided according to ridge counts (number of ridges between the 

core of the pattern to the delta) and ridge tracing (relative positioning of the deltas). Statistics in 

relation to these subclassifications are available. Table 3.3 presents two examples. 

 

187 Champod, C., C. Lennard, P. Margot, et al. Fingerprints and Other Ridge Skin Impressions. CRC Press, 2004.

188 Ibid.
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Table 3.3: Examples of statistics on subclassifications189

These data can assist fingerprint examiners in several ways. Because the frequencies of general 

patterns vary across the different fingers, the patterns offer information on which finger the latent 

print came from. In addition, during the Evaluation phase, a rare general pattern, such as a tented 

arch, can be weighted more than a common general pattern, such as a loop with a ridge count of 

between 11 and 20. 

L2D Features

The following two tables list frequencies, reported in studies prior to 1985, of the more 

discriminating L2D features (especially minutiae). 190 Not all types of minutiae were considered 

in each study.191

Study Authors, (Number of Prints) Number of Minutiae

Minutia Type Example

Gupta, (1,000 

ulnar loops) 

Unknown number 

of minutiae 

Osterburg et al., 

(39 fingerprints) 

8,591 cells of 1 

mm2

Lin et al.,

(76 fingerprints) 

14,280 minutiae

Ridge ending 7.50% 8.32% 9.60%

Bifurcation 

opening 

8.00% 3.82% 2.60%

Deviation 0.90% Not considered Not considered

Bridge 0.80% 1.22% Not considered

Island 2.50% 1.77% 0.99%

 

189 Ibid.

190 Stoney, D. “Measurement of Fingerprint Individuality.” In Advances in Fingerprint Technology, edited by Henry 

C. Lee and R.E. Gaensslen, 327–87. 2nd ed. CRC Press, 2001, p. 327. 191 A more recent analysis appears in Gutièrrez, E., V. Galera, J. Martínez, et al. “Biological Variability of the 

Minutiae in the Fingerprints of a Sample of the Spanish Population.” Forensic Science International, 172 (2007): 

98.
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Minutia Type Example Gupta Osterburg et al. Lin et al.

Interruption 0.90% 1.39% 1.20%

Hook 2.00% 0.75% 0.48%

Lake 2.50% 0.64% 0.17%

Dot 3.50% 1.51% 0.52%

Crossing 0.50% Not considered Not considered

Transversal 0.50% Not considered Not considered

Return 0.80% Not considered Not considered

Double 

bifurcation 

Not considered 0.14% 0.27%

Trifurcation Not considered 0.09% Not considered

Angular line Not considered Not considered 0.17%

Delta Not considered 0.20% Not considered

Other multiple 

occurrence

Not considered 3.55% Not considered

Absence of 

minutiae

Not considered 76.60% 83.90%

Table 3.4: Relative frequencies for different types of minutiae according to Gupta (1968),192 Osterburg 

et al. (1977),193 and Lin et al. (1982)194, 195

 

192 Gupta, S. “Statistical Survey of Ridge Characteristics.” International Criminal Police Review, 218 (1968): 130.
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Study Authors, (Number of Prints) Number of Minutiae

Minutia Type

Santamaria 

Beltran, (1,000 

fingerprints) 

Unknown 

number of 

minutiae

Kingston, (100 

ulnar loops) 

2,464 minutiae 

Sclove, (39 

fingerprints) 

2,536 minutiae 

Stoney, (412 

thumbs–distal 

area) 2,645 

minutiae

Ridge ending 53.40% 45.90% 49.70% 56.80%

Bifurcation

opening 

15.10% 34.10% 15.90% 43.20%

Bifurcation

closing

13.10% Not considered Not considered Not considered

Deviation 2.20% Not considered Not considered Not considered

Bridge 1.30% 1.90% 5.58% Not considered

Island 5.40% Not considered 10.30% Not considered

Interruption 1.60% Not considered Not considered Not considered

Hook Not considered Not considered 3.50% Not considered

Lake 4.20% 3.20% 2.63% Not considered

Dot 2.20% 8.30% 10.20% 5.30%

Crossing 0.22% Not considered Not considered Not considered

Transversal 1.30% Not considered Not considered Not considered

Return 0.024% Not considered Not considered Not considered

Double bifurcation Not considered Not considered 0.64% Not considered

Trifurcation Not considered Not considered 0.28% Not considered

Delta Not considered 1.70% 1.35% Not considered

Other multiple 

occurrence

Not considered 3.10% Not considered Not considered

Table 3.5: Relative frequencies for different types of minutiae according to Santamaria Beltran 

(1953),196 Kingston (1964),197 Sclove (1979-1980),198 and Stoney (1985)199

 193 Osterburg, J., T. Parthasarathy, T. Raghavan, et al. “Development of a Mathematical Formula for the Calculation 

of Fingerprint Probabilities Based on Individual Characteristics.” Journal of the American Statistical Association, 72 

(1977): 772.

194 Lin, C., J. Liu, J. Osterburg, et al. “Fingerprint Comparison I: Similarity of Fingerprints.” Journal of Forensic 

Science, 27, no. 2 (1982): 290. 195 Images adapted from Champod, C. Reconnaissance Automatique et Analyse Statistique des Minuties sur les 

Empreintes Digitales. PhD Thesis. Institut de Police Scientifique et de Criminologie, Université de Lausanne, 

Lausanne, Suisse, 1996.

196 Santamaria Beltran, F. “Une Nouvelle Méthode d’Évaluation des Points Caracteristiques des Crêtes Papillaires.” 

Assemblée Générale de la Commission International de Police Criminelle – Oslo. 24–29 June 1953; Santamaria 

Beltran, F. “Sous-Commission á la Dactyloscopie, Nouveaux Concepts d’Évaluation des Points Caractéristiques de 

F. Santamaria Beltran.” Assemblée Générale de la Commission International de Police Criminelle – Oslo. 25 June 
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Although this information could be helpful to an examiner, the data have significant limitations. 

There is no standardized nomenclature for the type of minutiae considered, how they were 

counted, how the absence of minutiae was evaluated, or how minutiae were distinguished from 

one another (e.g., when two bifurcations should be counted as two events or one double 

bifurcation event). This lack of standardized terminology applies across the entire fingerprint 

comparison field200 and makes comparison across these studies extremely challenging.

Also, the density of minutiae and their relative proportions depends greatly on their positioning 

on the papillary surface (especially in relation to core and deltas). For example, areas such as 

deltas and ridge flow regions along “type lines” tend to produce a higher number of minutiae. 

None of the studies took this into account. More recent models have begun to account for this 

phenomenon by using data-driven approaches that do not rely on pre-defined categories.

201 

L3D Features202

Limited statistical analyses of pores, or by extension, of L3D features of fingerprints, have been 

carried out for latent print comparisons in a forensic context. Ashbaugh indicated that 20 to 30 

corresponding pores between a latent print and a reference print would be sufficient for an 

individualization.

 

203 Roddy and Stosz concurred.204 However, their models relied on 

questionable independence assumptions205

 1953; Santamaria Beltran, F. “A New Method for Evaluating Ridge Characteristics.” Fingerprint and Identification 

Magazine, 36, no.11 (1955). 

 and, more importantly, did not take into account the 

potential lack of reproducibility of these features from one impression to the next. Parsons et al. 

investigated within-source variability and concluded that “due to contamination and inherent 

dependence, matching on 20 pores as has been previously suggested (Ashbaugh, 1983) appears 

to us overly optimistic. On the basis of this study, we would conjecture that good fingerprints 

197 Kingston, C. “Probabilistic Analysis of Partial Fingerprint Patterns.” Doctorate of Criminology diss., University 

of California, Berkeley, 1964.

198 Sclove, S. “The Occurrence of Fingerprint Characteristics as a Two-Dimensional Process.” Journal of the 

American Statistical Association, 74 (1979): 588; Sclove, S. “The Occurrence of Fingerprint Characteristics as a 

Two-Dimensional Poisson Process.” Communications in Statistics – Theoretical Methods, A9 (1980): 675. 199 Stoney, D. “A Quantitative Assessment of Fingerprint Individuality.” PhD thesis, University of California, Davis, 

1985.

200 Saviers, K. “Friction Skin Characteristics: A Study and Comparison of Proposed Standards.” Journal of Forensic 

Identification, 39 (1989): 157. 201 Champod, C. and P. Margot. “Computer Assisted Analysis of Minutiae Occurrences on Fingerprints.” 

Proceedings of the International Symposium on Fingerprint Detection and Identification. 1995; Neumann, 

Champod, Puch-Solis, et al., op. cit.; Egli, N. “Interpretation of Partial Fingermarks Using an Automated Fingerprint 

Identification System.” PhD thesis, École des Sciences Criminelles, University of Lausanne, 2009; Su, C. and S. 

Srihari. “Probability of Random Correspondence for Fingerprints.” Computation Forensics: Lecture Notes in 

Computer Science, 5718 (2009): 55. 202 This section comes from the supplementary report C. Champod provided on October 21, 2009, to The Fingerprint 

Inquiry of Scotland, available at www.thefingerprintinquiryscotland.org.uk/inquiry/2090.html, accessed April 22, 

2011.

203 Ashbaugh, D. “Poroscopy.” RCMP Gazette, 45, no. 2 (1983): 12. 204 Roddy and Stosz, op. cit. 205 Parsons, N., J. Smith, E. Thönnes, et al. “Rotationally Invariant Statistics for Examining the Evidence from the 

Pores in Fingerprints.” Law Probability & Risk, 7, no. 1 (2007): 1.
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with more than about 80 pores appear to have potentially strong evidential value using this 

extraction algorithm.” 206

Some biometric identification systems use pores and other features, such as dots and incipient 

ridges, to increase the efficiency of matching algorithms based on minutiae.207 However, highquality input prints increase the performance of such systems; L3D may have minimal added 

value for forensic latent prints of varying clarity and degrees of distortion. 

3.5.2 Recommendations and Best Practices

Data on minutiae rarity, density, and location should be important to latent print examiners in 

weighting different types of minutiae. These data can contribute to an expert’s informal 

judgment on the relative frequency of a given minutia. At the moment, surveys providing such 

information are available only for fingerprints, not for other forms of friction ridge areas such as 

palms or feet. Furthermore, the above data illustrate that a simple additive rule with equal weight 

for each minutiae within a fingerprint, such as a 12-point standard, ignores statistically important 

information. The data clearly show, as many examiners well recognize, that all minutiae are not 

equally useful for interpretation. For example, it may be seven times more common to see a ridge 

ending within a delta zone than a hook. The amount of discriminating information provided by 

the former is thus significantly less than that provided by the latter. Future research could better 

quantify the weight that should be assigned to different types of minutiae. Educating examiners 

about existing statistics, the limitations of these data, and the potential value of better statistics 

will advance the field.

Recommendation 3.5: Because statistical information plays a fundamental role in 

weighting latent print feature evidence, training should include the best available 

empirical information and should educate examiners about probabilistic reasoning in 

using that information. 

Given the current limitations in data and probabilistic models, other difficulties in weighting 

fingerprint evidence arise in some circumstances. Modern investigations often compare latent 

prints to exemplars from AFIS searches. Such exemplars raise the possibility of increased 

similarity to a latent print that actually comes from a different source. This phenomenon has been 

called “incidental similarity.”208

 

206 Ibid.

 Of course, the computer programs that generate candidates 

compare prints differently than human examiners do; nevertheless, when looking in a large 

database for those prints that bear the greatest similarity to the latent print in question, these 

207Chen, Y. and A. Jain. “Dots and Incipients: Extended Features for Partial Fingerprint Matching.” Paper presented 

at the Biometrics Symposium 2007; Kryszczuk, K., A. Drygajlo, and P. Morier. “Study of the Distinctiveness of 

Level 2 and Level 3 Features in Fragmentary Fingerprint Comparison.” Presented at the Proceedings of Biometric 

Authentication Workshop, ECCV, Prague, Czech Republic 2004, 124–33; Jain, Chen, and Demirkus, op. cit.; Zhao, 

Q., D. Zhang, L. Zhang, et al. “High Resolution Partial Fingerprint Alignment Using Pore-Valley Descriptors.” 

Pattern Recognition, 2009; Vatsa, M., R. Singh, A. Noore, et al. “Combining Pores and Ridges with Minutiae for 

Improved Fingerprint Verification.” Signal Processing, 89, no. 12 (2009): 2676–85. 208 For a discussion of this issue see Dror, I. and J. Mnookin. “The Use of Technology in Human Expert Domains: 

Challenges and Risks Arising From the Use of Automated Fingerprint Identification Systems in Forensic Science.” 

Law, Probability & Risk, 9 (2010): 47–67.
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programs could select a print from a nonsource that is far more similar to the latent print than 

examiners are accustomed to seeing.209 

An examiner whose idea of the necessary amount of information for a match comes from a nondatabase world may not be taking into account the possibility of incidental similarity that a large 

database carries with it. Unfortunately, no one has studied whether incidental similarity in a 

database context is a substantial problem,210 and it is tricky to recommend modifications to an 

interpretive system that is largely non-formalized. However, the Working Group believes that 

interpreting the quality of the evidence in such cases requires special care because the chances of 

finding a close nonmatch are higher. Such care might include strategies such as being more 

explicit about the weight assigned to individual features, using a higher threshold before reaching 

the conclusion for a match, or narrowing the tolerances for visual differences in appearance. 

These considerations lead to the following recommendation: 

Recommendation 3.6: When comparing latent prints to exemplars generated through 

AFIS searches, examiners must recognize the possibility and dangers of incidental 

similarity. Adjustments such as a higher decision threshold, stricter tolerances for 

differences in appearance, and explicit feature weighting need to be considered. 

Modifying quality assurance practices for this scenario also should be considered. 

3.5.3 Research Needs in Feature Weighting

There is a strong need for systematic studies pertaining to the reproducibility and discriminating 

strength of fingerprint features. More specifically, although the prevalence of particular L1D 

features is well documented, a more complete understanding of the dependencies in these 

features between fingers is desirable. Regarding L2D features, there is limited research that 

would allow a global assessment (without strong independence assumptions) of the strength of 

minutiae configurations. Likewise, the information power of L3D features is not fully understood 

nor has it fully been explored for forensic use. Limited systematic studies have been carried out 

on features such as creases, lines, and scars, which are useful to support the evaluation process 

when these features are present. These studies should take into account variables such as sex, 

finger number, pattern, and race. 

Such research is important when the examiner subjectively assigns weight to a set of features. 

Empirical studies on rarity can inform these experience-based judgments and help allow an 

examiner to assign appropriate weights to sets of features. Moreover, research exploring how 

examiners overestimate or underestimate the significance of features as a function of training, 

motivation, or context of the examination would be useful. 

 

209 Ibid.

210 But see Ulery, B., A. Hicklin, J. Buscaglia, et al. “Accuracy and Reliability of Forensic Latent Fingerprint 

Decisions.” Proceedings of the NAS. 2011. This experiment found relatively few false identifications for a sample of 

latent prints drawn in part from the results of AFIS searches, discussed supra Chapter 2). 
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3.6 Discrepancy Interpretation

In the friction ridge discipline, tolerance has been described as “the limits of how much 

distortion or difference is still considered within the parameters of agreement.”211 No two 

images, even if from the same source, will look identical. The question is the extent to which 

differences in the appearance of a particular friction ridge feature in the impression should be 

considered consistent with it coming from the same source as the exemplar print. 

3.6.1 Corresponding Stages in the Latent Print Examination Process Map

The decision regarding distortion occurs in several places in the latent print examination process. 

During the Analysis phase, an examiner observes not only the distinctive details of the latent 

print (step 210), but also analyzes the relevant distortion present in the latent print (step 220). 

Factors that affect the appearance of a latent print include the pliability of skin, condition of skin, 

deposition pressure, lateral movement, matrix (substance coating the ridges), substrate (surface 

on which the print is deposited), and development method.212 An important part of the initial 

analysis is the determination of how these factors might affect the latent print.

A similar, but separate, analysis is conducted on the known print (step 330). Pliability and 

condition of skin, recording method (e.g., ink or livescan), deposition pressure, lateral 

movement, and other factors can distort these impressions as well. 

In the Comparison phase, an examiner observes the latent and known prints side by side. The 

examiner must decide whether to tolerate the observed dissimilarities at all three levels of detail. 

If the two prints cannot be excluded based on L1D (step 500), the examiner continues the 

comparison to determine if the previously selected target group (step 290) falls within tolerance 

in the known print (step 510). If so, the examiner continues comparing additional detail. As 

dissimilarities are detected during the process, the examiner must determine if those differences 

are within tolerance for identification (step 600). 

3.6.2 Findings from Existing Research 

To assess distortion accurately, examiners must understand the flexibility of the skin, the limits 

of skin deformation, and other factors that may affect the appearance of a friction ridge 

impression. Figure 3.2 illustrates the range of distortion that can be expected on prints left by the 

same finger.

 

211 Ashbaugh, 1999, op. cit. 212 Ibid.
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Figure 3.2: Examples of skin distortion on prints of the same finger with arrows indicating location of 

the same minutiae in different impressions213

In developing automated fingerprint recognition systems, the biometrics industry conducted 

considerable research into the flexibility of skin.214 However, nonlinear distortion is complex. 

Although some research examines the effect of different pressures and motions on friction ridge 

impressions,215 examiners must predominantly rely on the knowledge gained during training and 

subsequent experience to recognize and interpret distortion. 

Under the one-dissimilarity doctrine, an examiner who does not know the cause of a dissimilarity

must exclude the two prints as having come from the same source.216 Under this rule, an 

incorrect interpretation of just one dissimilarity could lead to an erroneous exclusion. Some 

examiners do not accept the “one-dissimilarity” doctrine, believing it to be too strict given the 

complexity of impressions and the difficulty of distinguishing “true” dissimilarities from other 

distortions. Even among those examiners who do accept the rule in theory, it is not clear how 

rigorously it operates in practice. Faced with overwhelming detail in agreement and only one 

dissimilarity, examiners may have an understandable tendency to rationalize away the 

dissimilarity, even if they are not confident about its cause. Research does not establish whether 

such rationalization increases the accuracy of ultimate decisions or decreases it. It is certainly 

possible that a willingness to explain away difference in the face of a large amount of similarity 

would lead, on balance, to greater accuracy. Confirmation bias—the tendency to give more 

weight to confirming rather than disconfirming information—has been observed in many human 

endeavors (see Chapter 2). This type of bias also could occur if information from the known 

print influences the interpretation of the latent print. To minimize this effect, a thorough analysis 

of the latent print should be conducted before analyzing the known print. 

Although some literature demonstrates the effects that different distortions may have on friction 

ridge impressions,217

 

213 Fingerprint images adapted courtesy of the Instiut de Police Scientifique, Université de Lausanne.

little research has tested the examiner’s ability to accurately identify the 

214 Dorai, C., N. Ratha, and R. Bolle. “Dynamic Behavior Analysis in Compressed Fingerprint Videos.” IEEE 

Transactions on Circuits and Systems for Video Technology, 14, no. 1 (2004): 58–73.

215 Cowger, J. Friction Ridge Skin: Comparison and Identification of Fingerprints. CRC Press, 1992; Maceo, op. cit. 216 Thornton, J. “The One-Dissimilarity Doctrine in Fingerprint Identification.” International Criminal Police 

Review, 32, no. 306 (1977): 89–95.

217 Maceo, op. cit.
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different types of distortion. Such research is more common in other disciplines. In the medical 

field, for example, research has investigated how an expert develops the complex skill of 

interpreting X-ray images with a high degree of accuracy.218 Within the fingerprint field, the 

limited research has suggested that some assumptions about the causes of distortion have been 

wrong.219 

3.6.3 Recommendations and Best Practices

Given the importance of judgments that must be made about distortion in latent prints, it is 

critical that such judgments be documented clearly. As with other interpretive stages, examiners 

also need to document any modifications that are made after seeing the exemplar. Thus, 

Recommendations 3.1 and 3.2, described earlier in this chapter, are relevant to distortion. 

Likewise, steps to minimize cognitive biases are important for judgments regarding discrepancy. 

Therefore, Recommendation 3.3, that unnecessary information be kept from examiners, is also

important in this context.

3.6.4 Research Needs in Discrepancy Interpretation

Variability of Distortion

Examiners must predominantly rely on the knowledge gained during training and subsequent 

experience to recognize and interpret distortion. Underestimating the variability of distortion 

may lead to a false exclusion, while overestimating the variability may lead to a false 

identification. Studies to measure the variability of distortion and the extreme limits of distortion 

are needed. 

Identification and Interpretation of Distortion

An examiner’s ability to identify types of distortion has not been thoroughly studied. Research is 

needed not only to determine if an examiner’s working assumptions regarding the effects and 

degree of distortion have an empirical basis but also to determine if, or in what circumstances, a 

misattribution of distortion may lead to an incorrect conclusion. Experiments in which “ground 

truth” is known to the researchers (see Chapter 2) are appropriate for this purpose. 

Contextual Bias 

There has been little research in the fingerprint domain to determine the extent to which 

contextual information affects the interpretation of dissimilarities. More research is needed to 

determine when various context effects, such as confirmation bias, may lead to erroneous 

conclusions. 

3.7 Source Attribution 

Within the ACE-V process, three traditional options have been available to the examiner to 

signify findings. First, the examiner can conclude that the source of a known print is the source 

 

218 Sowden, P., I. Davies, and P. Roling. “Perceptual Learning of the Detection of Features in X-Ray Images: A 

Functional Role for Improvements in Adults’ Visual Sensitivity?” Journal of Experimental Psychology: Human 

Perception and Performance, 26, no. 1 (2000): 379–90.

219 Langenburg, G. “Deposition of Bloody Friction Ridge Impressions.” Journal of Forensic Identification, 58, no. 3 

(2008): 355–389.
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of the questioned print. In current practice, this identification is a claim that the latent matches 

the exemplar and that it would not match exemplars from anyone else in the world. Second, the 

examiner can conclude that the exemplar and the latent do not match and cannot share a common 

source, which is a categorical exclusion. Finally, the examiner may determine that the 

corresponding information in the latent and exemplar prints is inadequate to permit a conclusion. 

In this case, the examiner would state that the comparison was “inconclusive” and would provide 

no additional information about the chances that the two prints did or did not share a common 

source. The ultimate decision occurs near the end of the Process Map, at step 720 or 750, when 

the examiner determines whether the latent print matches the exemplar.
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3.7.1 Findings from Existing Research 

The Decision Process

Much has been written about the decision process by which a latent print examiner moves from 

feature detection and weighting, through a comparison with the exemplar, to reach a decision.220

Broadly speaking, an examiner uses an intuitive procedure to arrive at a subjective probability 

for source attribution. If this probability is high enough, the examiner declares an identification. 

If it is low enough, the examiner declares an exclusion, and if it is somewhere between these 

extremes, the examiner makes no inference (inconclusive). 

Bayesian decision theory offers a more complete, formal model of the intuitive decision-making 

process.221 According to this model, a latent print examiner should consider both the source 

probability and the costs and benefits (utilities) of correct and incorrect decisions. More 

specifically, the Bayesian examiner:

(1) Assesses the prior probability that source of the exemplar left the latent print. An 

examiner who purports to rely solely on the information in the prints rather than the 

context of the case or the other evidence against this individual would have no reason to 

distinguish this individual from anyone else on the planet capable of being where the 

latent print was found. An examiner who considers more details of the case might treat 

the source of the exemplar as equivalent to a random person drawn from a smaller 

population of conceivable suspects. Such reasoning leads to the reciprocal of the size of 

the relevant population as the prior probability. 

(2) Assesses the weight of the evidence as a function of the similarities and differences 

observed between the latent print and the exemplar. Formally, the weight is a likelihood 

ratio, as discussed below and in Chapter 1. Examiners may arrive at the weight intuitively 

(using their knowledge and experience) or by consulting data-driven likelihood models. 

However, these models currently use fewer features than a human examiner would, and 

they have other limitations.

(3) Computes the posterior probability of the proposition that the source of the exemplar left 

the latent print by combining the prior probability and the likelihood ratio according to 

Bayes’s rule (see Chapter 1).

(4) Combines the posterior probabilities with the utilities of the possible correct and 

incorrect decisions to reach and report the optimal decision. 

 

220 For an overview of the decision process and discussion of the philosophy of making individualization decisions, 

see generally Ashbaugh, 1999, op. cit.; Vanderkolk, J. “Levels of Quality and Quantity in Detail.” Journal of 

Forensic Identification, 51, no. 5 (2001): 461–68; Kwan, Q. “Inference of Identity of Source.” PhD thesis of 

Criminology, University of California, Berkeley, 1977. For discussion of the probabilistic nature of identification or 

individualization decisions see Champod, C. “Identification and Individualization.” In Wiley Encyclopedia of 

Forensic Sciences, edited by A. Moenssens and A. Jamieson, vol. 3, pp. 1508–11. J. Wiley & Sons, 2009. 221 Biedermann, A., S. Bozza, and F. Taroni. “Decision Theoretic Properties of Forensic Identification: Underlying 

Logic and Argumentative Implications.” Forensic Science International, 177 (2008): 120.
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Scholarship on the interpretation of forensic evidence argues that (1), (3), and (4) are in the 

exclusive province of the fact-finder (e.g., the jury in a trial) rather than the expert. 222 In this 

view, the examiner should report only the weight of the evidence (2), expressed either 

quantitatively or qualitatively. Today, however, in most jurisdictions, the examiner implicitly 

takes all the above steps. 

Regardless of whether the details of the Bayesian formulation provide an adequate descriptive or 

normative model of a latent print examination, the analysis is useful in clarifying the factors that, 

in some manner, must inform an identification decision. The weight of the evidence, the prior 

probability, the posterior probability, and the utilities of the possible decisions all bear on an 

examiner’s ultimate conclusion, but presenting that conclusion is not inherent in the examiner’s 

role of evaluating the latent print evidence. In particular, step (2) can be carried out via a 

likelihood ratio or through a less formal assessment that characterizes the Evaluation phase of 

ACE-V. Having performed this expert function, the examiner then can describe the weight of the 

latent print evidence to an investigator or fact-finder (see Chapter 6). 

Weight of the Evidence

Evaluation is the phase in a latent print examination during which the examiner assesses the 

totality of the features compared in the latent print and the exemplar. This can be thought of as 

the end result or the culmination of the stages described in earlier sections of this chapter. There 

are many ways for this assessment to occur, two of which are described below. 

The ACE-V process attempts to provide the framework from which a transparent threshold for 

an accurate and repeatable assessment of friction ridge skin can be established. The Evaluation 

phase refers to the final evaluation of whether the comparison results are sufficient to allow a 

determination, and if so, whether that determination is an identification or an exclusion. ACE-V 

does not, however, prescribe how this is done.223 Friction ridge examination by human beings is 

both human-resource intensive and subjective in the way in which the broadly defined ACE-V 

process is applied. There are no formal thresholds for any sufficiency determinations, and feature 

selection and weighting are matters of personal judgment. This is not to suggest that experts are 

poor at any of these tasks. Rather, it is simply to note the absence of objective criteria. Some 

countries take a less holistic approach and apply a minimum point standard. Although this does 

reduce subjectivity, it does not give adequate attention to variations in the rarity and clarity of the 

minutiae. Currently, the traditional ACE-V approach largely lacks validated, transparent 

thresholds. 

The likelihood ratio approach to evidence interpretation attempts to measure the total weight of 

evidence using information about the frequency with which different features are observed in the 

population. As explained in Chapter 1, the likelihood ratio is the probability of the data when one 

hypothesis is true compared to (divided by) the probability of the data when the competing 

hypothesis is true. Because it focuses attention on the support the data provide for the relevant 

hypotheses, the likelihood ratio is especially suitable for assessing the contribution of forensic 

 

222 E.g., Aitken, C. and F. Taroni. Statistics and the Evaluation of Evidence for Forensic Scientists. 2nd ed. John 

Wiley & Sons, 2004; Kaye, D., D. Bernstein, and J. Mnookin. The New Wigmore, A Treatise on Evidence: Expert 

Evidence. 2d ed. Aspen Publishers, 2011.

223 Mnookin, op. cit.
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findings in a balanced way.224 It applies regardless of the type of forensic evidence 

considered.225 The likelihood ratio invites forensic practitioners to assess the likelihood of the 

observed findings (the pattern of matching minutiae and other key observations) under the two 

different hypotheses that are relevant to the fact-finder (namely, that the prints came from the 

same source or different sources). 

In the case of latent print identification, the forensic findings are a set of concordances and 

dissimilarities (that can be reduced sometimes to a similarity score) of the comparison between 

the ridge detail features from the latent print and from an exemplar print from a potential source. 

The propositions under which the forensic findings are evaluated reflect the issues at hand; for 

example, either the friction ridge skin area of a potential source has truly left the latent print, or 

someone else from a relevant population of potential donors is actually the source of the latent 

print. Assessing the strength of evidence means answering two questions: (1) What is the 

probability of observing the similarities and dissimilarities if the two impressions come from the 

same source? (2) What is the probability of observing the similarities and dissimilarities if the 

two impressions come from different sources? 

The “likelihoods” that form the numerator and denominator of the likelihood ratio can represent 

an examiner’s subjective probabilities, or they can be determined from a data-driven 

probabilistic model. Without becoming mired in details, one can consider the conceptual steps 

involved in the formal modeling. To answer question (1), the similarity score of the latent print 

and the known exemplar images are positioned among all the possibilities of comparisons 

between the exemplar and distorted images of that precise source. Estimates of the distribution of 

similarity scores for distorted prints might be obtained either empirically (if sufficient control 

prints are available for that task) or by using a mathematical distortion model with parameters 

obtained from a large collection of prints taken from an individual. The location of the observed 

score within the estimated distribution indicates the probability of observing the level of 

agreement found between the latent print and the known exemplar, given the possibilities of 

distortion and the hypothesis that they come from the same source (the numerator). 

The denominator requires an estimate of the distribution of similarity scores when pairs of prints 

are drawn from different sources. The variation should be larger than that due to distortion alone, 

and the level of similarity should be low. The relevant question is whether the similarity score is 

more consistent with the type of variation that would be expected if the print originated from the 

same source than if it originated from another source. The next chapter reviews research on 

methods for automating the assessment of the likelihood ratio. 

One final topic associated with the likelihood ratio deserves attention. This concerns the 

interpretation of the likelihood ratio when an AFIS database search produces the candidate for 

comparison. There has been extensive debate, primarily in regard to DNA database trawls, about 

 

224 For a short introduction, see Champod, C. and I. Evett. “Evidence Interpretation: A Logical Approach.” In Wiley 

Encyclopedia of Forensic Sciences, edited by A. Moenssens and A. Jamieson, vol. 2, pp. 968–76. J. Wiley & Sons, 

2009. 225 Aitken, op.cit.; Kaye, Bernstein, and Mnookin, op. cit. The LR framework has been recommended in a standard 

adopted by all laboratories affiliated with the Association of Forensic Science Providers. Association of Forensic 

Science Providers. “Standards for the Formulation of Evaluative Forensic Science Expert Opinion.” Science and 

Justice, 49, no. 3 (2009): 161–64.
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how the search process affects the likelihood ratio. Most scholarship suggests that producing the 

suspect through a database search lowers the prior probability and raises the likelihood ratio.226

lowers the prior because there normally was 

no stronger reason to suspect the subject of 

the “hit” than there was to suspect other 

persons in the database.

It 

230 It raises the 

likelihood ratio primarily by eliminating (or 

least reducing the source probabilities for) 

all other individuals represented in the 

database.231 How to present the results of a 

database search most fairly remains 

debatable, but the concerns raised earlier 

about exemplars resulting from AFIS 

searches would be handled differently if the 

examiner were presenting both a prior 

probability and a likelihood ratio instead of 

collapsing these quantities into a subjective 

source attribution. 

Knowledge of Examiner Performance 

It can be difficult to create realistic scenarios 

in which examiners re-examine the same set 

of prints or in which they examine a set of 

prints for which the correct conclusion is 

known. As a result, controlled experiments 

that would illuminate the actual decisionmaking and source-attribution processes of 

latent print examiners during casework are 

unusual. The limited studies that have been 

done, however, suggest that variation in 

decisions occur, especially when contextual 

information is varied. Two noteworthy 

studies are discussed in Box 3.1. 

These experiments pose a real challenge. 

Experience is of enormous value and allows 

experts in a range of fields to operate at a 

high level. At the same time, experts can be 

prone to context effects. Although additional 

 

226 For a review of the DNA literature, see Kaye, D. “Rounding Up the Usual Suspects: A Legal and Logical 

Analysis of DNA Database Trawls.” North Carolina Law Review, 87, no. 2 (2009): 425–503.

227 Dror and Charlton, op. cit.; Dror, Charlton, and Peron, op. cit. 228 The experts were told that the prints were from the highly publicized misidentification of Brandon Mayfield in 

the Madrid train bombing case.

229 The study had no control group that unknowingly revisited earlier, challenging pairs of prints that they had 

determined to match. 

230 Kaye, op. cit., pp. 463 – 464.

231 Ibid., pp. 461 – 462.

Box 3.1: Studies on the Effect of Biasing 

Information 

In two studies in 2006, researchers collected 

casework that had been analyzed by experienced 

latent print analysts during their normal routine work 

several years earlier.227 The laboratory presented this 

casework to the analysts again in the ordinary flow of 

casework. In the first study, five examiners received 

a latent print and exemplar that they had previously 

classified as a match along with new contextual 

information that very strongly suggested that the pair 

did not match.228 Three of the five changed from their 

earlier conclusion of an identification to an exclusion. 

Another found the evidence inconclusive.229 

In the second study, six analysts received eight pairs 

of prints from earlier casework that was a mix of 

exclusion and individualization decisions. This time, 

the biasing information was weaker, and a control 

group that received no biasing contextual information 

was present. Only two of the six examiners made 

consistent decisions across all eight pairs of prints; 

the others changed one or more of the earlier 

decisions. Of the forty-eight presentations, there were 

six changes from the earlier judgments. In the biasing 

condition, there were three changes from 

individualization to exclusion, and one from 

individualization to inconclusive. In the control group 

of examiners who were not given any biasing 

contextual information, there was one change from 

individualization to exclusion and one from exclusion 

to individualization. The authors interpreted these 

outcomes as establishing “that fingerprint experts 

were vulnerable to biasing information when they 

were presented within relatively routine day-to-day 

contexts, such as corroborative (or conflicting) 

evidence of confession to the crime.” 
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study is clearly required, the evidence to date in the psychological literature, including the 

limited number of studies specific to latent print examination, supports Recommendation 3.3, 

which states that analysts should not be given contextual information that is not directly relevant 

to their analysis.

3.7.2 Recommendations and Best Practices

The discussion of the decision process, the way in which the weight of evidence is determined, 

and the possibility of errors all argue strongly that the common practice of claiming to uniquely 

identify an individual is not appropriate. As indicated above, a fingerprint identification was 

traditionally considered an “individualization,” meaning that the latent print was considered 

identified to one finger of a specific individual as opposed to every other potential source in the 

universe. However, the recent attention focused on this issue reveals that this definition 

needlessly claims too much, is not adequately established by fundamental research, and is 

impossible to validate solely on the basis of experience. Nor does fingerprint evidence have 

objective standards or a well-validated statistical model that can provide an objective measure of 

the strength of the fingerprint evidence in a given instance. Therefore, examiners should not 

claim to be able to exclude every other finger in the world as a potential source. Rather, an 

identification decision suggests a substantial enough similarity that the examiner believes that the 

two impressions originated from a common source. But whether any other finger in the world 

might also be able to leave an impression with a comparable amount of similarity is not fully 

known, and the examiner’s testimony should not suggest otherwise. Regardless of the specific 

words used to describe an identification, examiners should refrain from claiming that an 

identification means that they have excluded all other individuals in the world. 

Recommendation 3.7: Because empirical evidence and statistical reasoning do not 

support a source attribution to the exclusion of all other individuals in the world, latent 

print examiners should not report or testify, directly or by implication, to a source 

attribution to the exclusion of all others in the world.

As explained in Chapter 1, the Scientific Working Group on Friction Ridge Analysis, Study and 

Technology (SWGFAST) recently drafted language that eliminates this needlessly strong 

meaning of an identification (although SWGFAST also elected to continue to use the term 

“individualization” notwithstanding its long association with this idea). The proposed 

SWGFAST draft states, “Individualization of an impression to one source is the decision that the 

likelihood the impression was made by another (different) source is so remote that it is 

considered as a practical impossibility.”232 

Eliminating the previous “to the exclusion of all others” language from the definition is a step in 

the right direction. However, the new text raises two concerns. First, it is unnecessary for an 

examiner to reach conclusions about what is a “practical impossibility.” Although fingerprints 

are clearly highly discriminating, until further research permits better validated statements about 

probabilities, neither experience nor statistical modeling justifies conclusions about what is or is 

 

232 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Draft for Comment: Standards for 

Examining Friction Ridge Impressions and Resulting Conclusions (To Replace: Friction Ridge Examination 

Methodology for Latent Print Examiners, Version 1.01, and Standards for Conclusions, Version 1.0). Version 1.0. 

Scientific Working Group on Friction Ridge Analysis, Study and Technology, August 2010, p. 4.
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not practically possible across a population of billions of individuals (and billions times billions 

of possible pairs of prints). Second, given that the word “individualization” has been associated 

precisely with the “to the exclusion of all others” claim of universal individualization based on a 

premise of general uniqueness (see Chapter 1), it is potentially problematic and confusing to 

attempt to redefine it by fiat. Using alternative terminology might be a superior solution to 

attempting to “legislate” a new and slightly modified meaning to a much-criticized term and 

theory. 

In July 2010, the membership of the International Association for Identification (IAI) adopted 

Resolution 2010-18, allowing members to give qualified opinions if supported with a statistical 

model “accepted as valid by the IAI.”233 However, the IAI also stated that it does not endorse 

any models as ready for casework or introduction into the courtroom. The resolution is another 

important step in the right direction, and the Working Group supports further movement in this 

direction. 

Until statistical models are implemented, concerns remain about over-expressing the evidence 

(see Chapter 6). In addition, there are legitimate concerns about under-expressing, or not 

expressing at all, the wealth of evidence that can be found in the large grey zone between 

“identification” and “exclusion.” In the future, it seems likely that examiners will be required to 

provide more nuanced information than the current, narrow range of allowable conclusions. In 

time, it should be possible to provide quantitative measures in the form of likelihood ratios or 

posterior probabilities (see Chapters 4 and 6). Even if this does not happen, qualified conclusions 

consistent with existing knowledge should be permitted. 

The difficult problem here is to find a balance between the two views of how to report 

fingerprint evidence, since both views have strengths and weaknesses. If absolute conclusions 

are not allowed, then one is left only with reported conclusions that allow for more than one 

possible donor of a latent print, as is the case with other types of forensic evidence canvassed in 

Chapter 6. Conversely, there may be instances in which a single source attribution is warranted 

based upon the theory of local uniqueness outlined in Chapter 1. If qualified opinions are not 

allowed, then one may be keeping from fact-finders evidence that exists in the grey continuum 

between absolute source attribution and absolute exclusion. There is often evidence that is 

strongly associative to a source, based upon high likelihood ratios (either explicitly or implicitly 

derived), but that does not rise to the level at which an examiner feels comfortable providing a 

traditional “identification” conclusion. This evidence and the decision to withhold it are typically 

not communicated to the fact-finders. This all-or-nothing approach keeps potentially critical 

evidence from fact-finders based on the profession’s need to maintain categorical opinions of 

“identification” or “exclusion.” Alternatively, there may be instances (for example, when dealing 

with fully rolled fingerprints, identification of deceased individuals, and ten-print examinations) 

when categorical decisions such as “identification” or “exclusion” are completely warranted, 

justified by the overwhelming availability of discriminating features, and practical for the 

circumstances. Finding the balance between these issues is not easy, especially in the absence of 

data showing which approach is most appropriate for the circumstances and which approach will 

not confuse or mislead the fact-finders.

 

233 International Association for Identification. IAI Resolution 2010-18. International Association for Identification, 

July 16, 2010.
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The Working Group could not resolve the important questions surrounding whether, or when, 

latent print examiners should be permitted to testify to probabilities rather than absolute 

categories, nor did it endeavor to determine what form probabilistic testimony should take. These 

issues will continue to grow in both salience and importance in the coming years. Hence, the 

Working Group strongly recommends ongoing attention to this issue. 

Recommendation 3.8: The friction ridge examiner community and other experts should 

determine under what circumstances a qualified rather than an absolute conclusion is 

warranted.

3.7.3 Research Needs in Source Attribution

Research in the latent print domain in past decades has largely been centered on automated 

fingerprint identification systems and physical and chemical detection techniques. Very little 

research, until the last few years, has centered on human performance in pattern recognition and 

interpretation. Much more research is needed not only to validate ideas being put forward today 

but also to expand understanding further. 

• Research and testing to develop greater knowledge about error rates for latent print 

examination must be undertaken. While a single error rate for the field is neither 

desirable nor achievable, it is critical to develop more knowledge about error rates, what 

affects them, and the extent to which they are correlated to the relative difficulty of 

comparisons (see Chapter 2). Indeed, it is possible that such work will help define levels 

of complexity. 

• It will be important to understand what influences affect not only the ultimate decisions 

of examiners but also their decision-making thresholds. It is entirely possible that bias 

influences decision thresholds, but not decision outcomes, in easy latent print 

comparisons. At what point does this impact on thresholds change outcomes? 

• With expanded knowledge on thresholds must come research that investigates whether 

considering certain features makes examiners more vulnerable to inaccurate decisions.

• More research is needed into the relationship between risk and cost to examiners when 

making decisions. For example, does the cultural default position of law enforcement and 

its relationship with forensic practitioners create an environment in which latent print 

examiners shun the inconclusiveness of evidence in favor of more definitive conclusions 

that are more conducive to current law enforcement expectations? Research will better 

inform whether there needs to be a change in the culture of forensic support services in 

relation to their policing partners.

• The confidence associated with decision making in latent print examination should be 

studied to see if confidence levels are consistent when making identifications as opposed 

to exclusions. It will also be important to determine under what circumstances a qualified 

conclusion would be warranted, whereby a lack of strong confidence in a particular 

decision based upon a latent print comparison might be better expressed as “consistent 

with.” In other words, when might it be appropriate to offer a conclusion that is less 

emphatic?
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3.8 The Need for Research

The previous sections each ended with a list of research topics relevant to the particular 

interpretative stage. This section characterizes in broad terms the types of research that are 

required and incorporates a final recommendation about the importance of the federal 

government finding a mechanism to fund a research program. 

The research topics identified throughout the chapter can be broadly categorized into three types: 

(1) developing metrics or measurements that characterize key elements of the interpretive 

process, (2) assessing the reliability of measures or determinations, and (3) determining the 

factors associated with different performance levels. 

3.8.1 Developing Metrics

Across the interpretive stages, there is a need to carefully define elements being used by 

examiners in a manner that allows the processes to be studied quantitatively. Examples include 

developing a way to characterize selected features (perhaps by location and degree of 

confidence), developing a series of indicators of sufficiency, conducting additional work on the 

frequency of features in different populations, and perhaps ultimately developing a measure of 

the complexity of a particular comparison. 

3.8.2 Assessing Reliability, Reproducibility, and Validity 

A process for making measurements or decisions is reliable when the outcomes are repeatable 

and reproducible, both within and across examiners. It is important that feature selection, 

sufficiency determination, feature weighting, judgments regarding distortion, and ultimate 

decisions be reproducible. An examiner repeatedly presented with the same sets of prints should 

obtain the same interpretive conclusions (intra-examiner reliability), and different examiners also 

should be able to obtain the same results (inter-examiner reproducibility). For many, these two 

concepts are at the heart of the ongoing discussion about the desirability of research to reaffirm 

the consistency of latent print judgments. Some research has been conducted on this issue,234 but 

more is needed. 

Accuracy is whether the determinations made by the analyst correctly express the true state of 

the world. This accuracy can be measured in various ways, as discussed in Chapter 2. A final 

term, validity, also refers to accuracy but extends further to encompass the issue of whether the 

measurements, judgments, and decisions being made are appropriate for their common uses. 

Thus, validity is a relative term. The polygraph is a valid means of detecting stress, but its 

validity as a device to detect conscious deception is much more doubtful. Whether ACE-V does 

what its practitioners claim it does and whether the resulting decisions are adequately supported 

by scientific knowledge are questions about validity. 

 

234 Langenburg, G. “A Performance Study of the ACE-V Process: A Pilot Study to Measure the Accuracy, Precision, 

Reproducibility, Repeatability, and Biasability of Conclusions Resulting from the ACE-V Process.” Journal of 

Forensic Identification, 59, no. 2 (2009): 219–57; Evett and Williams, op. cit.; Dror and Charlton, op. cit.
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3.8.3 Explaining Variations in Performance 

The final element of a research program would attempt to explain observed variations in 

reliability or accuracy. A key question that underlies much of the discussion in this chapter is 

how the complexity of a comparison impacts the reliability of the determined conclusions. There 

are, however, as many types of analyses as one can imagine. Relating performance to the 

individual characteristics of the examiner, including physical characteristics, training completed, 

and aspects of the working environment, may help supervisors determine strategies for 

recruitment and training to optimize performance. This list is not comprehensive. It argues 

strongly, however, as do other chapters in this report, for an extensive research program. 

Recommendation 3.9: The federal government should support a research program that 

aims to: 

a. Develop measures and metrics relevant to the analysis of latent prints; 

b. Use such metrics to assess the reproducibility, reliability, and validity of various 

interpretive stages of latent print analysis; and 

c. Identify key factors related to variations in performance of latent print 

examiners during the interpretation process.

 

3.9 Summary

For each interpretive stage of latent print examination, this chapter offers recommendations and 

best practices to help ensure the accuracy and transparency of the interpretive processes. The 

chapter describes and defines the multiple critical interpretive stages that are part of every latent 

print comparison. The Working Group based its analysis and recommendations on the current 

state of knowledge established by published research regarding the interpretive stages and on the 

implications of this research for potential concerns and pitfalls that may arise in the interpretive 

process. 
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Chapter 4: Looking Ahead to Emerging and Improving Technology

Introduction and Scope

Latent print examiners use online databases, digital enhancement software, and other types of 

technology to assist with the Analysis, Comparison, Examination, and Verification (ACE-V) 

process. Combining these tools with the examiner’s own expertise can make investigations more 

reliable and easier to explain to juries. This chapter discusses how these and newer technologies 

can automate complicated and work-intensive parts of the process and thereby reduce human 

error. In particular, the chapter addresses the following technology-related questions: 

• Fingerprint and palm print databases at the federal, state, and local levels can be searched 

through automated fingerprint identification system (AFIS) databases, which saves 

examiners from manually searching through hundreds of exemplars looking for close 

matches. How can these systems (and the training provided to examiners in their use) be 

improved to provide greater confidence in the results and more value to examiners? 

• Digital scanning devices known as livescan are frequently used to capture exemplar 

prints and to submit them to automated systems. This process allows high-quality digital 

images to be stored in central databases. How can this technology be improved? 

• When comparing digital exemplars to digital latent prints, examiners can enhance the 

images to clarify minute details. What are the best practices for enhancement? The 

process of enhancement can be challenged in court, so examiners must understand and be 

able to explain the technology. 

• When testifying, examiners should qualify their conclusions instead of stating an 

exclusion or identification in absolute terms. With modern computational power, 

researchers have implemented various probabilistic models to allow examiners to 

quantify the similarities between two prints and to assess the implications of these 

similarities. How can these models be used, and what are their long-term implications?

• How can automated systems assist in ascertaining the quality and quantity of the features 

in a latent print? 

• How do examiners interact with new technological tools? How can technology-training

programs be more effective for examiners at all career levels? 

4.1 Automated Fingerprint Identification Systems

AFIS databases exist at federal, state, and local levels.235

 

235 See generally Moses, K. “Automated Fingerprint Identification System (AFIS).” The Fingerprint Sourcebook. 

National Institute of Justice, 2011.

 The Integrated Automated Fingerprint 

Identification System (IAFIS), managed by the Federal Bureau of Investigation (FBI), holds 

most of the fingerprint sets and other identification records collected in the country, both from 

criminal and civil sources. In addition, every state either has its own AFIS or shares an AFIS 

with other states. Many localities, especially large metropolitan areas, have their own systems as 
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well. All of these automated systems have capabilities such as latent print searching, electronic 

image storage, and fingerprint image transmission, and some include palm prints as well.

236 In 

criminal cases, IAFIS searches through millions of criminal entries and returns results in about 

10 minutes. 237 

4.1.1 Training

The companies that supply AFIS software and hardware provide general training on using the 

system, but they do not clearly define which latent prints are most suitable for database searches. 

With experience, latent print examiners may develop an understanding of what makes a latent 

print of “AFIS quality” for a particular system, but receiving formal instruction and training in 

making these determinations would be more efficient. 

Likewise, AFIS vendors typically do not provide training on how to encode a latent print to 

maximize the match capabilities of the system. An AFIS search merely provides a list of 

exemplars with the highest similarity scores, as determined by a proprietary algorithm. Latent 

print examiners often use trial and error, entering the same latent print multiple ways to see the 

effect on the resulting candidate list. Vendors should expand their training programs to include 

instruction in the most effective methods for encoding. 

In addition, more education on the meaning of the AFIS scores could be useful. Some examiners 

use rank or score as a filter, hoping to avoid wasting time on fruitless comparisons. Thus, many 

examiners will not look beyond rank 5 or 10 (sometimes by policy). Some examiners use a 

system-specific score as a cutoff. Others look at candidates based upon the differences between 

scores, believing that any score that is substantially greater than that for the next candidate is 

worth comparing, whereas a series of candidates with very similar scores are much less likely to 

be matches. Some examiners look at all the candidates, assigning some weight to a high AFIS 

score or rank. Still other examiners entirely disregard score and rank information. There is some 

evidence that knowing the rank of an AFIS candidate influences the judgments of some 

examiners, but it is not clear whether this knowledge benefits or hinders the ACE-V process. 238

On the basis of the available research, we can make no recommendation on whether the 

examiner should be blinded to the scores or ranks of AFIS-generated exemplars when 

conducting comparisons and evaluations. Regardless of the advisability of knowing the scores or 

ranks of these exemplars, however, latent print examiners who frequently work with exemplars 

from AFIS searches should have a clear understanding of how the system works and the meaning 

and limitations of AFIS scores and ranks. 

 

236 Ibid.

237 Federal Bureau of Investigation. “Integrated Automated Fingerprint Identification System.” Accessed November 

25, 2011. http://www.fbi.gov/about-us/cjis/fingerprints_biometrics/iafis/iafis. 

238 See Dror, I., K. Wertheim, P. Fraser-Mackenzie, et al. “The Impact of Human-Technology Cooperation and 

Distributed Cognition in Forensic Science: Biasing Effects of AFIS Contextual Information on Human Experts.” 

Journal of Forensic Sciences (forthcoming). 
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4.1.2 AFIS Algorithms

AFIS algorithms could be expanded to match prints to account for the diagnostic value of the 

positions at which minutiae are located. Exploiting this information might improve AFIS 

searches, and research into the utility of using the additional information might assist in the 

development of probabilistic models (as discussed in section 4.3.1). 

4.1.3 Interoperability 

The 2009 report of the National Research Council239 recommends improving the interoperability 

of AFIS systems among states and the FBI. Searching multiple databases would help states 

identify criminals who have been fingerprinted in other states. Because the National Institute of 

Standards and Technology has established a separate working group on this topic, this Working 

Group did not pursue this issue. 

4.1.4 Other Skin Surfaces

Automated search technology can be applied to impressions from all friction ridge skin areas, 

such as palmar (palm or digital joint) or plantar (toe or foot) friction ridges. These impressions 

sometimes are searched if the capability exists within the automated identification system of the 

investigating department. Nonetheless, exemplars from these areas are collected less frequently, 

and it may prove difficult to construct large databases for these impressions. 

Recommendation 4.1: The federal government should support research programs to 

improve automated fingerprint identification systems. Such programs could address the 

following issues:

a. Expanding the algorithms used to match prints to account for the fact that the 

diagnostic value of minutiae depends on the region in which they are located;

b. Making fingerprint and palm print databases interoperable among local, state, 

and federal automated identification systems; and

c. Increasing compatibility between automated identification systems and other 

latent print software tools, including digital enhancement programs, probability 

calculation programs, and automated quality assessment programs. 

4.2 Digital Images

4.2.1 Livescan Systems

Police departments (and other government agencies) traditionally recorded known exemplars by 

inking a person’s ten fingers and rolling them onto a paper ten-print card. Larger departments 

now use livescan technology to digitally capture finger and palm prints.240

 

239 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009.

This inkless method 

captures digital images of exemplar prints, which can be transmitted together with demographic 

data and mug shots to a central location. The system rejects the print if the quality falls below a 

240 See e.g., Moses, op. cit. 
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certain threshold. When properly maintained and used by adequately trained personnel, livescan

can improve both the quality and speed of the ten-print collection process. 

However, livescan technology can be improved. For example, livescan can produce distorted 

images of the flow of friction ridge skin because of the process of recording a three-dimensional 

object on a two-dimensional surface. Some livescan (and almost all automated fingerprint 

identification) systems compress images. This practice causes critical details in the friction ridge 

impression to be lost, even when the images are decompressed. Most AFIS and livescan systems 

use images scanned at 500 pixels per inch. Although this standard satisfies the FBI’s Electronic 

Fingerprint Transmission Specification standard, such images, especially if highly compressed, 

may not capture all Level 3 Detail (L3D) that would be desirable for examiners performing 

comparisons. Because of these limitations, many examiners prefer inked prints over livescan

images for final comparisons. 

4.2.2 Digital Enhancements

The use of digital processing and enhancement is now routine in latent print analysis. If properly 

used to remove background distractions that are not part of the friction ridge detail, digital 

enhancement can improve both the examiner’s ability to analyze the image and the jury’s ability 

to understand the evidence. Yet filtering an image also could create artifacts that an examiner 

might mistake for minutiae. Figures 4.1 and 4.2 provide examples of applying filters to digital 

images.

Figure 4.1: Example of a color replacement filter to remove color from a playing card241

 

241 Images reproduced and adapted courtesy of Robert Garrett, past president and chairman of the board of the 

International Association for Identification. 
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Figure 4.2: Example of filters used to adjust color levels and to reverse the colors

242

Because of the possibility of artifacts, judges should not unquestioningly accept an expert’s 

claim that an enhanced image is accurate. There is a growing judicial recognition that the party 

introducing enhanced images as trial exhibits must be able to defend the enhancements in each 

case.243 In State v. Swinton,

244 the Connecticut Supreme Court upheld the admission of a 

photograph of a digitally enhanced bite mark; however, the court rejected the prosecution’s 

argument that the court should accept the enhancement as easily as the original photograph. The 

court accepted the enhancement because the expert testified “in specific detail as to the process” 

of programming the enhancement software. Moreover, the court rejected overlays created with 

Adobe Photoshop because the witness could not explain the use of the program for that purpose. 

The California Supreme Court issued a similar opinion in People v. McWhorter.245 In that case, a 

defense expert prepared an enhanced image of a window. In upholding the exclusion of the 

testimony, the court noted that the expert “could not identify the computer program he used to 

enhance or ‘electronically emboss’ the image in question, nor could he satisfactorily explain the 

full nature of the process he used to create it.”246

Although Swinton and McWhorter may have insisted on more thorough foundations than are 

typical, the decisions highlight the importance of clearly understanding the process and benefits 

of digitally enhancing images. Under the usual rules for scientific evidence and for 

authenticating photographs, an expert must be able to demonstrate that the software can 

accurately enhance the original image and that it was used properly. 

The Scientific Working Group on Imaging Technology (SWGIT) has proposed best practices for 

the acquisition, storage, and processing of images.247

 

242 Images reproduced and adapted courtesy of Robert Garrett, past president and chairman of the board of the 

International Association for Identification. 

Underlying the guidelines are several basic 

principles. In particular, forensic service providers should validate latent print enhancement 

technologies prior to use in casework. To maintain an appropriate audit trail, the providers 

243 State v. Hartman, 754 N.E.2d 1150 (Ohio 2001). 244 State v. Swinton, 847 A.2d 921 (Conn. 2004).

245 212 P.3d 692 (Cal. 2009). 246 Ibid, 726. 247 See International Association for Identification: Scientific Working Group on Imaging Technology (SWGIT). 

Accessed April 23, 2011. http://www.theiai.org/guidelines/swgit/index.php.
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should retain the unenhanced image and should track any digital enhancements made to 

subsequent copies. Examiners should make it clear in their documentation and testimony that an 

image has been enhanced. If the proffered image is enhanced, the proponent should make the 

earlier versions of the image available to the opposition before trial. If the examiner cropped the 

image, the deleted material should be available for inspection. The proponent should not be 

permitted to claim that the original, unaltered image is unavailable due to the enhancement 

software that was used. 

In many cases, examiners employ enhancement techniques during their analyses but submit the 

unaltered images to the court as evidence.248 Forensic service providers should ensure every 

examiner has received training in the technology used to assist in analysis. Moreover, the 

provider should announce guidelines for the use of such technology. Forensic services providers 

should follow the best practices the proposed by SWGIT for the acquisition, storage, and 

processing of images. Developers should validate enhancement technologies used in latent print 

processing. The laboratory using the technology should validate the technology in its work 

environment and should retain the original, unenhanced image. 

4.3 Probabilistic Models to Assess Latent Print Evidence

As discussed in Chapters 3 and 6, examiners often offer opinions as to the source of the latent 

print in absolute terms. Indeed, as noted in Chapter 6, a 1979 resolution of the International 

Association for Identification announced that it was professional misconduct for an examiner to 

use the term “probable” in a final opinion.249 Although Resolution 2010-18 declares that the 

prior resolution was “not consistent with advancements,”250 most courts still allow the examiner 

to opine in absolute terms and to attribute a particular fingerprint impression to a single 

individual’s finger to the exclusion of all other persons in the world. These courts do not demand 

that the examiner quantify the extent of any uncertainty (see Chapter 6). 

However, Chapter 3 recommends against testimony in this form. There is always some non-zero 

probability that some skin other than the defendant’s produced the latent print. Even when this 

probability is so small that a source attribution is warranted, the opinion would be more precise 

and complete if the examiner could provide an estimate of this probability. Models to allow and 

support this qualified response are being developed and validated. 

4.3.1 Probabilistic Models

The last 100 years have seen many efforts to characterize the significance of similarities between 

pairs of fingerprints. Some models have tried to demonstrate the discriminating power of latent 

 

248 Annotation, Admissibility and Weight of Fingerprint Evidence Obtained or Visualized by Chemical, Laser, and

Digitally Enhanced Imaging Processes, ALR 5th Alert, 110 (2003): 213. 249 International Association for Identification. “Resolution VII.” Identification News, 29 (August 1979). 250 International Association for Identification. IAI Resolution 2010-18. International Association for Identification, 

July 16, 2010.
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print evidence, other models have aimed at proving the uniqueness of latent print impressions, 

and still others have focused on quantifying the weight of the latent print evidence in the case.251

Probability models date back to Galton’s 1892 model.252 Modern efforts to determine the 

probability of correct latent print identification are based upon determining the locations of 

minutiae,253 of minutiae and ridges,254 and even of pores255 (see Figure 4.3). These models 

incorporate measures of tolerance in accounting for skin distortion and the degradation of crime 

scene impressions. To date, research into probability models has been limited to the distal 

segments of the fingers; the remainder of the friction ridge skin has not been considered. By 

estimating the probability of random correspondence for any given set of latent print features 

rather than the probability of all of the features of a complete exemplar, the calculations reflect 

the quantity of information present in the latent fingerprint. 

Figure 4.3: An example of some minutiae locations in a fingerprint256

Although the modern models represent a major improvement over the early efforts, most models 

assume independence among minutiae.257

 

251 Stoney, D. “Measurement of Fingerprint Individuality.” In Advances in Fingerprint Technology, edited by Henry 

C. Lee and R.E. Gaensslen, 327–87. 2nd ed. CRC Press, 2001; Langenburg, G. “Scientific Research in the Forensic 

Discipline of Friction Ridge Individualization.” In The Fingerprint Sourcebook. National Institute of Justice, 2011..

 That is, they assume that the occurrence of one 

minutia has no relationship to the occurrence of any other set of minutiae. However, minutiae 

might not be independent. Some data (see Chapter 3) indicate that the frequency of certain 

252 Galton, F. Finger Prints. 1892. Reprint, William S. Hein & Co., 2003. 253 Dass, S., Y. Zhu, and A. Jain. “Statistical Models for Assessing the Individuality of Fingerprints.” Proceedings. 

Fourth IEEE Workshop on Automatic Identification Advanced Technology, 2005. 254 Chen, Y. and A. Jain. “Beyond Minutiae: A Fingerprint Individuality Model with Pattern, Ridge, and Pore 

Features.” In Proceedings, International Conference on Biometrics (ICB), Advances in Biometrics, Third 

International Conference, Alghero, Italy, June 2–5, 2009; Su, C. and S. Srihari. “Evaluation of Rarity of 

Fingerprints in Forensics.” In Proceedings of Neural Information Processing Systems Conference, Vancouver, 

Canada, December 2010. 255 Chen and Jain, op. cit.

256 Fingerprint image adapted from the Royal Canadian Mounted Police. Fingerprint Manual. Chapter 2. Royal 

Canadian Mounted Police, 1990.

257 Pankanti, S., S. Prabhakar, and A. Jain. “On the Individuality of Fingerprints.” IEEE Transactions on Pattern 

Analysis and Machine Intelligence, 24, no. 8 (2002): 1010.
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minutiae varies depending on the location of the minutiae within the larger pattern. One study 

reports that in 100,000 randomly chosen fingerprints of exemplar quality, there is only a 10−14 

probability that some pair of them will match in regard to both minutiae and ridge shape.258

Without the assumption of independence, however, the computed probability could be orders of 

magnitude higher.259 

Likelihood Ratio Models 

Some scientists have developed models that provide likelihood ratios in biometric verification260

and in forensic friction ridge analysis.261 The likelihood ratio combines information on the 

similarity and rarity of features in a pair of prints. In one approach, the initial step is to 

quantitatively compare an appropriate set of features characterizing Level 1 Detail (L1D) such as 

ridge flow, Level 2 Detail (L2D) such as minutiae, and minute Level 3 Detail (L3D) details such 

as pores between the two fingerprint images. This process of marking features can be entirely 

manual or partly or fully automated. If a single number is used as an overall measure of 

similarity and rarity, its probability distributions in two populations can be considered. One 

probability distribution comes from a large number of images derived from the same finger; the 

other comes from a sample of images derived from the fingers of different individuals. The 

likelihood ratio indicates how many times more probable it is to find characteristics with the 

overall similarity score when the known exemplar and the latent come from the same finger than 

when they come from different fingers. (For further explanation of likelihood ratios, see 

Chapters 1, 3, and 6.) 

Studies of likelihood ratio models have produced at least three important findings.262

 

258 Su, C. and S. Srihari. “Generative Models for Fingerprint Individuality Using Ridge Models.” In Proceedings 

19th International Conference on Pattern Recognition, Tampa, Florida, December 8–11, 2008.

 First, when 

fingerprint impressions come from the same source, they display a large number of matching 

features, and the likelihood ratio is large. Second, same-source impressions infrequently yield 

likelihood ratios less than one when the two impressions have the same origin. Conversely, 

likelihood ratios greater than one seldom appear when the two prints have different origins. 

Thus, research with data sets in which ground truth is known demonstrates that the models 

usually point to the correct conclusion. In addition, these data sets can be used to estimate error 

rates for making all decisions based strictly upon a particular threshold for the likelihood ratio. 

Finding much larger likelihood ratios for impressions from the same source than for impressions 

from different sources supports the claim that fingerprints contain highly discriminating 

259 Recent work relaxing the independence assumption is Su and Srihari, 2010, op. cit. 260 Bazen, A. and R. Veldhuyis. “Likelihood-Ratio-Based Biometric Verification.” In IEEE Transactions on Circuits 

and Systems Video Technology, 14 (2004): 85; Gonzalez-Rodriguez, J., J. Fierrez-Aguilar, D. Ramos-Castro, et al. 

“Bayesian Analysis of Fingerprint, Face and Signature Evidences with Automatic Biometric Systems.” Forensic 

Science International, 155 (2005): 126. 261 Champod, C. and P. Margot. “Computer Assisted Analysis of Minutiae Occurrences on Fingerprints.” In 

Proceedings of the International Symposium on Fingerprint Detection and Identification, 1995, 305-18; Neumann, 

C., C. Champod, R. Puch-Solis, et al. “Computation of Likelihood Ratios in Fingerprint Identification for 

Configurations of Any Number of Minutiae.” Journal of Forensic Sciences, 52, no. 1 (2007): 54 – 64; Neumann, C., 

C. Champod, R. Puch-Solis, et al. “Computation of Likelihood Ratios in Fingerprint Identification for 

Configurations of Three Minutiae.” Journal of Forensic Sciences, 51, (2006): 1255; Egli, N., C. Champod, and P. 

Margot. “Evidence Evaluation in Fingerprint Comparison and Automated Fingerprint Identification Systems—

Modelling Within Finger Variability.” Forensic Science International, 167 (2007): 189 – 95.

262 Champod and Margot, op. cit.; Neumann, Champod, Puch-Solis, et al., 2007, op. cit.; Neumann, Champod, PuchSolis, 2006, op. cit.; Egli, Champod, and Margot, op. cit. 
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information. Finally, different configurations of the same number of minutiae produce different 

likelihood ratios, depending on the spatial relationship between the minutiae. In many instances, 

configurations with few minutiae have larger likelihood ratios than configurations with more 

minutiae. It follows that a simple count of matching minutiae is an imprecise measure of the 

similarity of two prints. 

Future Probabilistic Models 

Additional work should be done to further demonstrate the reliability and validity of latent print 

probabilistic models. This work will necessitate studies with large-scale, representative 

databases. Furthermore, once a model is validated, careful thought must be given to the best 

method of communicating its output to the actors in the criminal justice system (see Chapter 6). 

To facilitate the development of probabilistic models, a research database could be created by 

removing personal identifiers from digital images in AFIS databases. Anonymous versions of 

criminal DNA databases have been used for statistical research,263 and there is no insuperable 

legal obstacle to doing the same with fingerprint records in the possession of the government.264

The only social or psychological risk to individuals whose prints are in the existing databases is 

that the de-identified images from a criminal file somehow would permit a researcher to discover 

who has been arrested for or convicted of unspecified crimes. However, the researchers have no 

means to link an image with a name, and even if they could do so, that an individual has a 

criminal conviction normally is not private information. Therefore, AFIS database administrators 

should take the simple step of de-identifying a large set of digital images for research purposes. 

This will permit the validation of probabilistic models and will facilitate studies into the 

frequencies of various fingerprint features (discussed in Chapter 3). 

Recommendation 4.2: To facilitate the validation of probabilistic models and other 

statistical research, the federal government should create large, anonymous databases 

of exemplars and latent prints.

More generally, with suitable support for modern research, some of the probability models that 

researchers are currently developing could be added to the examiner’s toolkit in the near future. 

To prepare for such models, the latent print examiner community should formulate workflow 

guidelines to transition the models from the research setting to the forensic laboratory and should 

begin training examiners in elementary probability and statistics to enable them to interpret the 

output of the models. Recommendations 3.5 and 3.9 in Chapter 3, concerning federal support of 

research and educating examiners about statistical methods, are pertinent here.

4.3.2 Admissibility

Once validation studies are published, opinions based upon a probability model could be 

proffered in court. If opposing counsel objects and challenges the validity of the models, the 

courts would need to determine the admissibility of the evidence. As discussed in Chapter 6, the 

leading standards in the United States for making this determination are the scientific validity 

 

263 Kaye, D. “Trawling DNA Databases for Partial Matches: What Is the FBI Afraid Of?” Cornell Journal of Law 

and Public Policy, 19 (2009): 145.

264 See 5 U.S.C. § 552a(b)(5); 42 U.S.C. § 3789g(b).
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standard of Daubert v. Merrell Dow Pharmaceuticals, Inc.265 and the general acceptance 

standard of Frye v. United States.

266 Under these standards, the proponent of the output of a 

statistical model or an examiner’s opinion based on this model would have to show that the 

model is valid or generally accepted in the scientific community. It is premature to predict which 

probabilistic models will be validated and proven useful in court; the optimal model may prove 

to be one that has yet to be proposed. It is possible that multiple opinions based upon different 

probability models as well as the output of the model itself would be admissible. 

4.3.3 Implications of the Validation of a Probabilistic Model 

A useable probabilistic model could significantly affect the methods of latent print examination. 

First, the model might require new metrics in latent print images, that is, the documentation and 

measurement of new features. Some of the current models rely on measurements that many 

examiners do not take, such as the distance between friction ridge features. If measurements and 

the computation can be automated, then the use of the model could reduce the risk of human 

error in making and using such measurements. 

Additionally, judicial acceptance of testimony based upon a probabilistic model could change the 

presentation of examiners’ opinions in court. Chapters 3 and 6 urge that examiners clearly 

communicate the qualified nature of an opinion to the court. Reliance on statistical models would 

enable the examiner to acknowledge the uncertainty of the conclusion or to dispense with a 

binary opinion. 

Lastly, judicial acceptance of probabilistic models would not force examiners to become 

statisticians, but it would require them to be familiar with certain statistical concepts to testify to 

probabilities or to an opinion based upon a probabilistic model. Specifically, examiners would 

need to understand uncertainty, variability, conditional probabilities, probability distributions, 

and likelihood ratios. They should also be able to explain these concepts to judges and juries. 

Statisticians and the latent print examiner community can collaborate to design a training 

program for examiners. 

Recommendation 4.3: The latent print examiner community should expand the training 

of examiners in elementary probability theory to enable examiners to properly utilize 

the output of probabilistic models. 

4.4 New Technologies for Latent Print Examination

4.4.1 Automated Quality Assessment

Early in the examination process, the examiner must decide whether the latent print is suitable 

for further analysis—this is the Analysis phase in the ACE-V process. In the experience of the 

Working Group, this initial quality assessment of the latent print is often the weak link in the 

analytical process, as examiners could make two types of errors. In the first type of error, the 

examiner prematurely discards a print that should be deemed suitable for further analysis and 

 

265 509 U.S. 579 (1993).

266 293 F. 1013 (D.C. Cir. 1923).
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comparison, possibly resulting in a missed identification or exclusion. In the second type of 

error, the examiner continues to evaluate a latent print that he ought to have deemed unsuitable 

for further processing. This outcome results in wasted time and might even contribute to an 

erroneous identification. 

Currently available automated systems can assist in various steps within the Analysis phase. 

Automated systems can measure the distance between certain features in two images. They can 

also generate probabilities for such distances under the assumptions that the image of the latent 

print comes from a finger known to have produced an exemplar and that the latent comes from a 

finger of a randomly selected individual represented in a reference set of exemplars from many 

individuals. Such conditional probabilities might be used in their own right or to corroborate or 

contradict the judgment of a human examiner. Thus, an automated technique employing a 

validated algorithm for judging the quality of an image and its suitability for forensic 

identification would be extremely useful. 

There have been attempts to develop automated quality assessment technology.267 Although the 

efforts have so far met with limited success,268 automation seems possible. Given a suitable way 

to calibrate the extent and clarity of the features in the latent and exemplar prints, an objective 

quality measure could be calculated. This is not to say that the task will be easy. The challenges 

to creating an automated quality assessment procedure are threefold: (1) identifying the most 

critical elements to assess the quality of an image, (2) choosing a metric to assess each element 

selected, and (3) combining these assessments to determine when the quality is sufficient to 

warrant further effort. Just as prints vary in clarity and completeness, examiners vary in 

experience and skill. An impression deemed unsuitable by an examiner of lesser skill might be 

considered useful by a more seasoned examiner. In addition, if an algorithm indicates that a 

latent print is suitable, an examiner might feel pressured to go beyond the normal comfort level 

to reach a definite conclusion.269 This pressure may be compounded by the widespread 

assumption that if a print is judged to be of value, a comparison with an exemplar print should 

always permit the examiner to either identify or exclude. Furthermore, there is no guarantee that 

algorithms can be developed to mimic this type of human interpretation, especially the 

evaluation of L3D, or that examiners can develop an effective strategy for employing such 

technology. 

Ultimately, the research may yield the conclusion that automation cannot improve the initial 

quality assessment. Any investigation into the possibility of automating this stage ought to be 

conducted with these risks and challenges in mind. Nevertheless, because the Analysis phase is 

so important to the overall examination, a concerted effort to automate the quality assessment 

step, at least partially, is worthwhile. 

 

267 Hicklin, A., et al. “Latent Fingerprint Quality: A Survey of Examiners.” Journal of Forensic Identification, Jul–

Aug 2011, 385–417.

268 Egli, Champod, and Margot, op. cit.; Neumann, C., I. Evett, and J. Skerrett. “Quantifying the Weight of Evidence 

from a Forensic Fingerprint Comparison: A New Paradigm.” Journal of the Royal Statistical Society, Series A, 

forthcoming; Neumann, Champod, Puch-Solis, et al., 2006, op. cit.; Neumann, Champod, Puch-Solis, et al., 2007, 

op. cit.; Perlin, M., J. Kadane, and R. Cotton. “Match Likelihood Ratio for Uncertain Genotypes.” Law, Probability 

& Risk, 8 (2009): 289. 269 Dror, I. and J. Mnookin. “The Use of Technology in Human Expert Domains: Challenges and Risks Arising 

From the Use of Automated Fingerprint Identification Systems in Forensic Science.” Law, Probability & Risk, 9 

(2010): 47–67.
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Recommendation 4.4: The federal government should continue funding research into 

automation of the initial quality assessment step in latent print analysis.

4.4.2 Latent Print Examiner Attitudes toward New Technology

Some veteran examiners began their careers well before the advent of modern technologies such 

as AFIS, livescan, and digital enhancement. Younger examiners have likely worked with these 

technologies throughout their professional lives. Understandably, examiners vary in their 

comfort level in using the most sophisticated technologies. Some examiners prefer to use a 

magnifying glass or loupe to study hard copies of the images. Others routinely compare 

on-screen images. 

Manufacturers should take two steps to make examiners comfortable with new technologies. 

First, manufacturers should ensure that new products are as usable as reasonably possible (see 

Chapter 7). Second, manufacturers should expand their training programs. Traditionally, training 

programs have focused primarily on the technical aspects of the instrumentation. Training 

programs also should confront the fact that some examiners may subconsciously resist new 

technologies that supplant the methods that they have been using for decades. In addition to 

teaching examiners the specific mechanics of using the new technology, the program ought to 

attempt to enhance the trainee’s general technology skills. Chapter 8 provides more information 

on training improvements. 

Forensic laboratory staff members should collaborate with manufacturers on the development of 

training programs and usable tools. As the consumers of the tools and training programs, the 

laboratory staff members have unique perspectives that can make a significant contribution to 

both development projects. Chapter 7 addresses this topic of holistic and user-centered design in 

more detail.

4.5 Summary

Technology can help latent print examiners fully analyze evidence and reach reasonable 

conclusions that they can defend in court. Some of these technologies, such as AFIS, livescan, 

and digital enhancement software, already exist; however, there is room to improve these 

products, and further research should be conducted to enhance these technologies. 

In addition, research into probability models that allow examiners to qualify their conclusions 

should continue. Quantitative measures of fingerprint similarity can and have been developed. 

The likelihood ratio for a measurement indicates how many times more probable it is for a pair 

of prints from the same source to possess the measured degree of similarity than it is for a pair 

from different sources to be that similar. By expressing the strength of the evidence in this way 

and noting uncertainties in the values of the likelihood ratios, experts leave it to the judge or jury 

to use the degree of similarity, along with the other evidence in the case, to decide whether a pair 

of prints has a common source (see Chapter 6). Research into models that generate valid 

probabilities should continue, and examiners should receive training to explain relevant 

probabilities and statistics in court. Finally, research should be conducted into software to assist 

examiners with quantity and quality assessments for latent prints. 
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Examiners and other forensic laboratory staff members should work with technology 

manufacturers to ensure that the products are designed for ease of use and that training programs 

are sufficient. Training programs should consider those examiners who may be reluctant to rely 

on new technology processes that augment their traditional methods of moving through the 

Analysis, Comparison, and Evaluation phases. Research into new and valuable technologies and 

the further validation of existing technologies and methods will have a positive, long-term 

impact on the latent print community.
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Chapter 5: Reports and Documentation

Introduction and Scope

This chapter concerns written records of the results of friction ridge skin impression 

examinations in criminal investigations. The process of documenting an examination can help 

address human factors issues that could lead to inferential errors. Best practices for documenting 

the examination and producing a summary report for investigators and the judicial system 

increase the likelihood that the conclusions of the examiner are accurate and supported and will 

be used appropriately. 

The two recommendations presented here are intended to increase the level of comprehensibility, 

transparency, and completeness of written (or electronic) records without imposing impractical 

and undue demands on the often over-burdened agencies and examiners. In developing these 

recommendations, the Working Group was guided by, but not confined to, existing standards and 

guidelines of professional organizations and accrediting bodies. 

Throughout the chapter, the generic term “record” denotes both the written report and the 

underlying documentation, such as bench notes and copies of images. This chapter does not 

attempt to specify precisely how to allocate the information between the report and the residual 

documentation, but it does list the minimum information that should appear in the summary 

report. It also urges that reports use clearly defined terms so as to be most useful to criminal 

investigators, lawyers, judges, and juries. To provide the rationale for the recommendations, the 

chapter begins with a description of the value and purposes of contemporaneous documentation 

of examinations and the preparation of written reports. 

5.1 Reporting and Documentation for Quality Assurance and Control

A written report of an examination of friction ridge skin impressions presents the examiner’s 

findings, indicates how the examiner arrived at these findings, and refers to more detailed 

documentation of the process. These records serve both scientific and legal functions. From the 

scientific standpoint, proceeding according to a well-defined, uniform protocol and 

contemporaneously recording the results can improve interpretation (see Chapter 3). In addition, 

“thorough documentation of this process allows for the transparency required for competent 

reviewers to determine that the data and case information have been appropriately 

considered.”270 “By ensuring that the examiner has followed the prescribed procedure, and by 

permitting external review, reports are a quality [assurance and] control mechanism.”271

These considerations lead to the overarching principle that a report and supporting notes or 

materials should document the examination process in sufficient detail so that a reviewing expert 

could verify the validity of the examiner’s assessment of the evidence. This principle is 

 

270 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Strengthening Forensic Science in 

the United States: A Path Forward, Position Statement. Scientific Working Group on Friction Ridge Analysis, 

Study and Technology, 2009.

271 American Bar Association. Standards for Criminal Justice: DNA Evidence. 3rd ed. American Bar Association, 

2007, p. 72.
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incorporated in Recommendation 3.1 (Chapter 3) and endorsed by scientific working groups 

from a variety of forensic disciplines, including friction ridge analysis,272 firearms and toolmarks 

analysis,273 and drug analysis.274 It leads to more specific recommendations that further define 

the minimum level of detail required for quality assurance and control purposes. Before 

presenting these more detailed recommendations, it is helpful to consider the role that reporting 

and documentation play in the legal system. 

5.2 Legal Purposes of Written Records

5.2.1 Pretrial Uses of Reports

Expert reports convey useful information to the prosecution and defense before trial. “Because 

the reports are discoverable, they assist attorneys in preparing for trial and thus render effective 

representation.”275 Accordingly, one federal magistrate judge recently urged that 

to ensure that defense counsel can make any challenges to the admissibility of 

toolmark identification evidence and that courts may conduct hearings to resolve 

these challenges based on sufficient record, the Government should be required to 

strictly and timely comply with its [pretrial discovery] obligations regarding the 

opinions to be offered by firearms examiners in sufficient detail and sufficiently 

far in advance of motions deadlines or trials as to enable defense counsel to 

evaluate the conclusions and bases, determine whether to engage experts to test 

them, and if appropriate, challenge them.276 

Moreover, due process principles require the prosecution to disclose information that is 

“favorable to the accused”277 and “material either to guilt or to punishment,”278 as well as 

“evidence that the defense might have used to impeach the government’s witnesses by showing 

bias or interest.”279 The prosecution is responsible for disclosing all such information, even if it 

is in the hands of the law enforcement agency.280

disclosure obligations and avoid accusations of hiding relevant evidence. As in other fields,

 Making a good faith effort to ensure reports 

contain all known exculpatory and impeachment material helps the government comply with its 281

such accusations are not unheard of in regard to latent print examinations.282

 

272 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standard for the Documentation of 

Analysis, Comparison, Evaluation, and Verification (ACE-V) (Latent). Version 1.0. Scientific Working Group on 

Friction Ridge Analysis, Study and Technology, February 2010. 273 Scientific Working Group for Firearms and Toolmarks. Guidelines for the Standardization of Comparison 

Documentation. Scientific Working Group for Firearms and Toolmarks, October 2010.

274 Scientific Working Group for the Analysis of Seized Drugs. Scientific Working Group for the Analysis of Seized 

Drugs (SWGDRUG) Recommendations. Revision 5.1. Scientific Working Group for the Analysis of Seized Drugs, 

January 2011.

275 American Bar Association, op. cit., p. 73 (note omitted). 276 United States v. Willock, 696 F.Supp.2d 536, 570 (D.Md. 2010). 277 Brady v. Maryland, 373 U.S. 83, 87 (1963). 278 Ibid. 279 Ibid. 280 See Kyles v. Whitley, 514 U.S. 419, 437 (1995); Pierce v. Gilchrist, 359F.3d 1279 (10th Cir. 2004). 281 Tiscareno v. Anderson, 639 F.3d 1016 (10th Cir. 2011), vacated in part, 421 Fed. Appx. 842 (10th Cir. 2011); 

Pierce v. Gilchrist, 359 F.3d 1279 (10th Cir. 2004). 
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Finally, although the forensic expert cannot control the actions of police or prosecutors, the 

expert may have an ethical obligation to avoid such practices as “preparation of reports 

containing minimal information in order not to give the ‘other side’ ammunition for 

cross-examination,” “reporting of findings without an interpretation on the assumption that if an 

interpretation is required it can be provided from the witness box,” and “omitting some 

significant point from a report to trap an unsuspecting cross-examiner.”283

5.2.2 Trial Uses of Reports

In addition to their pretrial uses, reports can assist experts who testify. Although there can be 

obstacles (discussed below) to introducing the report itself into evidence, documentation of the 

chain of custody of the evidence is crucial, and the written materials can be consulted to refresh a 

witness’s recollection. In addition, when a report is admitted as an exhibit, it becomes part of the 

trial record, which allows the jury to rely on the statements in it and to consult it during jury 

deliberations. Admission thus can streamline the presentation and can reduce the time needed to 

present the results during trial. Indeed, laboratory reports sometimes are admitted by stipulation 

in lieu of live testimony.

When a prosecutor offers a report into evidence, however, a defendant can object that it is 

hearsay. Although a laboratory report offered into evidence to prove the facts recorded in it is

technically hearsay, in many jurisdictions laboratory reports are admissible under an exception to 

the hearsay rule.284 In addition, even if the hearsay objection prevails and the report is not 

evidence in its own right, the expert who prepared the report or another expert may be permitted 

to rely on it as part of the basis for the testifying expert’s own opinion.285

If the prosecutor does not present the author of the report for cross-examination at trial, a 

defendant also can object that the absence of the witness violates the constitutional right to 

confront one’s accusers. The Confrontation Clause of the Sixth Amendment prevents the 

prosecution from introducing “testimonial” statements accusing the defendant without producing 

 282 See, e.g., Edwards, H. “Solving the Problems that Plague the Forensic Science Community.” Jurimetrics Journal 

of Law, Science, and Technology, 50 (2009): 9; Henson, S. “Brady Violations by DPS Fingerprint Examiners? Is 

Fingerprint Examination even Science?” Grits for Breakfast. Blog post, October 9, 2010. Accessed November 25, 

2011. http://gritsforbreakfast.blogspot.com/2010/10/brady-violations-by-dps-fingerprint.html.

283 Lucas, D. “The Ethical Responsibilities of the Forensic Scientist: Exploring the Limits.” Journal of Forensic 

Sciences, 34 (1989): 724. Examples of such expert advocacy by forensic serologists can be found in Garrett, B. 

Convicting the Innocent: Where Criminal Prosecutions Go Wrong. Harvard University Press, 2011. 284 The hearsay issue is somewhat intricate. Congress expressly excluded police reports prepared for criminal 

prosecutions from the public records exception to the hearsay rule in Federal Rule of Evidence 803(8)(B). One line 

of cases reasons that this provision implies that crime laboratory reports also are outside the scope of the related 

Rule 803(6) business records exception to the hearsay rule. United States v. Oates, 560 F.2d 45 (2d Cir. 1977). Other 

federal circuits are more willing to apply the business-records exception. E.g., United States v. Baker, 855 F.2d 

1353, 1359 (8th Cir. 1988). State court opinions also are conflicting. Compare Commonwealth v. Carter, 932 A.2d 

1261 (Pa. 2007) (admissible hearsay), with People v. McDaniel, 670 N.W.2d 659 (Mich. 2003) (inadmissible 

hearsay). Some states have enacted specific rules to overcome the hearsay objection to crime laboratory reports. 

E.g., Massachusetts General Laws, ch. 111, §13; People v. McClanahan, 729 N.E.2d 470, 472 (Ill. 2000) (referring 

to Illinois statute). 

285 E.g., Pendergrass v. State, 913 N.E.2d 703, 709 (Ind. 2009); Kaye, D., D. Bernstein, and J. Mnookin. The New 

Wigmore, A Treatise on Evidence: Expert Evidence. 2nd ed. Aspen Publishers, 2011. § 4.6.
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the author of the statements for cross-examination. In Melendez Diaz v. Massachusetts,

286 the 

Supreme Court applied this doctrine to sworn statements from laboratory analysts at the state 

Department of Public Health. Their “certificates of analysis”287 contained “only the bare bones 

statement that ‘the substance was found to contain: Cocaine.’ At the time of trial, petitioner did 

not know what tests the analysts performed, whether those tests were routine, and whether 

interpreting their results required the exercise of judgment or the use of skills that the analysts 

may not have possessed.”288 The Court determined that because the “analysts’ statements [were] 

prepared specifically for use at petitioner’s trial, [they] were testimony against [the] petitioner, 

and the analysts were subject to confrontation under the Sixth Amendment.”289 Thus, whether or 

not the certificates were inadmissible as hearsay, the state should not have relied on them without 

giving the defendant the opportunity to cross-examine the analysts themselves.

Because reports of friction ridge examinations conducted at the request of criminal investigators 

are also testimonial, these reports cannot serve as a complete substitute for the courtroom 

testimony of the examiners if the defendant objects to their introduction. Nevertheless, written 

records can facilitate the presentation of the prosecution’s case and make the trial more efficient. 

Melendez Diaz noted that “it is not the case that anyone whose testimony may be relevant in 

establishing the chain of custody, authenticity of the sample, or accuracy of the testing device 

must appear in person as part of the prosecution’s case.”290 Portions of a laboratory report or 

documentation detailing these matters might be considered non-testimonial. Moreover, the 

defendant’s right to confrontation does not prevent the prosecution from presenting a laboratory 

report with the testimony of the analyst or examiner. Indeed, if the analyst is unavailable to 

testify, the report still may be admissible if the “defendant had a prior opportunity for 

cross-examination.”291 In addition, there may be cases in which an expert witness who did not 

perform the original examination can testify to or rely on the contents of a report from the expert 

who did.292 Finally, like the hearsay rule, “the right to confrontation may, of course, be waived, 

including by failure to object to the offending evidence ... .”293

 

286 Melendez Diaz v. Massachusetts, 129 S. Ct. 2527 (2009).

In fact, jurisdictions are free to 

adopt statutes or rules that enable a prosecutor to secure such a waiver by giving pretrial notice 

of the intent to use the report as long as “the defendant is given a period of time in which he may 

287 Ibid., p. 2531. 288 Ibid., p. 2537. 289 Ibid., p. 2540.

290 Ibid., p. 2532, note 1. 291 Ibid., p. 2531. 292 Compare People v. Williams, 939 N.E. 2d 268, 270 (Ill. 2010), cert. granted sub nom. Williams v. Illinois, 80 

U.S.L.W. 3003 (U.S. June 28, 2011) (allowing surrogate testimony from a DNA analyst at a state laboratory who 

compared a crime-scene DNA profile generated by a private laboratory to the profile from defendant’s blood sample

and determined that they matched), with Bullcoming v. New Mexico, 131 S.Ct. 2705 (2011) (“Surrogate testimony” 

about a defendant’s blood alcohol level was inadmissible when the forensic analyst who conducted the gas 

chromatography, wrote a report, and signed a certificate of analysis did not testify but was not shown to be 

unavailable to testify and the witness who testified in his place worked at the same laboratory and was familiar with 

its procedures but had not participated in the testing or supervised the original analyst.)

Of course, the Confrontation Clause does not bar testimony from a fingerprint examiner who re-examines a 

set of images to form an independent expert opinion. The significant questions pertain only to presenting or relying 

on “testimonial statements” about the images made by other examiners who are not themselves made available for 

cross-examination. See Kaye, Bernstein, and Mnookin, op. cit., § 4.10.

293 Melendez Diaz, 129 S. Ct. at 2535 n. 3.
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object to the admission of the evidence absent the analyst’s appearance live at trial.”294 However,

a more complete report could reduce the chance that the defense will demand the presence of the 

examiner and could enhance the chance that a laboratory supervisor or other analyst can testify at 

a trial if the examining analyst is unavailable.

In sum, the value of comprehensive written records in trial and pretrial proceedings reinforces 

Recommendation 3.1, calling for contemporaneous documentation that makes “the interpretive 

process as transparent as possible” and “sufficient to permit another examiner to assess the 

accuracy and validity of the initial examiner’s assessment of the evidence.” In addition, the fact 

that the readers of an examiner’s report in a case scheduled for trial are likely to be lawyers, 

judges, or jurors prompts a related recommendation directed specifically at the examiner’s 

summary report: 

Recommendation 5.1: The report of the examination should ensure that the findings 

and their limitations are intelligible to non-experts.

This recommendation finds support in the views of legal and scientific organizations, such as the 

American Bar Association295 and the National Research Council,

296 as well as forensic science 

working groups and organizations, such as the European Network of Forensic Science 

Institutes297 and the Scientific Working Group for the Analysis of Seized Drugs.298 The 

European Network, for example, explains that

the reports of forensic investigations will be read by a wide variety of individuals, 

many of whom will have little knowledge of science. They may have to be read 

aloud in courts of law to inform judges and advocates and, in some jurisdictions, 

members of a jury. Reports must, therefore, be written as clearly and 

unambiguously as possible. Great care must be taken to ensure that all details 

relating to the examinations undertaken, and the scientific rationale on which the 

examinations are based, are described in language that can be understood by 

nonscientists.299 

 

294 Ibid., p. 2541. If the defendant does object, it appears that the state cannot place the burden of calling the witness 

on the defendant. Briscoe v. Virginia, 130 S.Ct. 1316 (2010). 295 American Bar Association, op. cit., Standard 16-3.3(c). 296 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009, p. 186; National Academy of Sciences, National Research Council Committee on Scientific Assessment 

of Bullet Lead Elemental Composition Comparison. Forensic Analysis: Weighing Bullet Lead Evidence. National 

Academies Press, 2004, p. 110.

297European Network of Forensic Science Institutes Standing Committee for Quality and Competence. Performance 

Based Standards for Forensic Science Practitioners. European Network of Forensic Science Institutes Standing 

Committee for Quality and Competence, July 2004.

298 Scientific Working Group for the Analysis of Seized Drugs. Supplemental Document SD-1 for Part I, A Code of 

Professional Practice for Drug Analysts. Recommendation 2.3.1. Scientific Working Group for the Analysis of 

Seized Drugs, October 2004. 

299 European Network, op. cit., Activity I.
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5.3 Minimal Contents of a Report

There is no hard and fast line between the information that should be recorded in reports versus 

contemporaneous, supporting documentation. One laboratory could include considerable detail 

in a report prepared for police or litigants, while another might store much of the same 

documentation elsewhere and write a shorter report that simply refers to the underlying 

documentation. Therefore, the Working Group does not propose a one-size-fits-all division of the 

necessary information. Instead, the outline below contains the minimum content of a report and 

indicates what additional information should be recorded, either in the report or in related 

documentation. This chapter’s appendices offer sample reports of varying length and detail. 

 

Broadly speaking, a report should describe the items submitted to the latent print examiner, how 

the examiner processed these items, and how the examiner reached any conclusions. Although it 

has been said that “case documentation is not complete if the record-keeping process does not 

begin at the crime scene,”300 and a full report certainly could describe the entire chain of 

evidence, the focus here is on the processing, examination, and conclusions about the material 

after it is delivered to a latent print examiner. The essential contents of a report on these phases 

of evidence assessment are listed at the conclusion of this section in Recommendation 5.2, and 

the appendices to this chapter present sample reports. The recommendation covers such matters 

as reporting on each step of the Analysis, Comparison, Evaluation, and Verification (ACE-V) 

process; noting non-essential, domain-irrelevant information known to the examiner (if any); 

noting the existence of documentation outside the report itself; and presenting results and 

defining terms.

5.3.1 Images of Friction Ridge Impressions

Friction ridge impressions on surfaces may be examined on that surface, developed from that 

surface, or placed into another format (such as a photograph or scan) for analysis and 

comparison. When a development process was used, or when the image was copied into another 

format, the report should define the process that was used and indicate that an image of the 

developed friction ridge impression was retained. 

5.3.2 List of Comparisons 

Latent prints can be compared to other latent prints to see if the same individual was present at 

both locations. They can be compared to a ten-print card or other exemplar from a known 

individual. In addition, exemplars from an individual whose identity is in question can be 

compared to exemplars from known individuals. The report should list which images were 

compared to one another. 

Traditionally, latent prints have been compared with ten-print cards for pre-existing suspects in a 

case. The creation of large databases of computer-searchable images permits comparisons to 

individuals culled with automated fingerprint identification system (AFIS) software (Chapter 4). 

 

300 Peterson, P., C. Dreyfus, M. Gische, et al. “Latent Prints: A Perspective on the State of the Science.” Forensic 

Science Communications, 11, no. 4 (October 2009).
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If an AFIS search has been conducted, the report should specify the results. A record of the AFIS 

candidate list should be retrievable. 

5.3.3 Method and Conclusions

Just as a report should indicate how latent prints were made visible, it also should state the 

procedure used to make comparisons between friction skin impressions and to draw conclusions 

from these comparisons.301 The conventional procedure for associating latent and known prints 

involves the ACE-V process described in Chapter 1. Traditionally, the outcome of ACE-V has 

been expressed in terms of three possible categories: individualization, exclusion, or 

inconclusive.302 Nonetheless, scientific research or reasoning does not limit reported results to 

these three categories.303 A more finely graded set of categories is possible (see, for example, 

Chapter 9), and the computer-based methods described in the preceding chapter are another way 

to measure the features of prints and the degree of similarity between pairs of prints. As 

automated systems advance and are further validated with large data sets, they will be useful in 

conjunction with (or conceivably, at some time in the future, instead of) ACE-V. But, whatever 

procedures are employed to draw inferences from the evidence—ACE-V or otherwise—the 

report should designate them and should frame the conclusions in a manner that is accurate and 

scientifically appropriate. 

5.3.4 Limitations

For the sake of lay readers, a report may contain some general warnings that indicate its limits. 

For example, if no comparisons were made, the report might note that the absence of any usable 

latent prints, or even any smudges, does not mean that the surface was never touched. If the 

examiner associates the latent print with a known finger, the report might observe that, standing 

alone, this association does not indicate how, why, or when the latent print was deposited. 

Statements like these are included in reports of the Federal Bureau of Investigation (FBI). They 

are not necessary to present the results of an examination or to document how it was conducted, 

but they may be helpful for some readers. 

In addition, if there are significant reasons to question any conclusions, these should be noted.304

As the Scientific Working Group for the Analysis of Seized Drugs concluded, forensic analysts 

have the professional responsibility to present both written and oral “advice ... in a clear and 

objective manner”305

 

301 Compare American Society of Crime Laboratory Directors. Guidelines for Forensic Laboratory Management 

Practices. American Society of Crime Laboratory Directors, 1987.

—a duty that entails “considering and providing alternative explanations or 

302 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standards for Conclusions. 

Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, September 2003.

303 Budowle, B., J. Buscaglia, and R. Perlman. “Review of the Scientific Basis for Friction Ridge Comparisons as a 

Means of Identification: Committee Findings and Recommendations.” Forensic Science Communications, 8 

(January 2006); Haber, L. and R. Haber. Challenges to Fingerprints: A Guidebook for Prosecution and Defense and 

Examiners. Lawyers and Judges Publishing Co., 2009. 304 European Network, op. cit., Standard I1(c); NAS, NRC, Committee on Identifying the Needs of the Forensic 

Science Community, op. cit., pp. 21-22; SWGDRUG, 2004, op. cit., Recommendation 2.3.1. But see Scientific 

Working Group on Materials Analysis. Forensic Human Hair Examination Guidelines. Scientific Working Group 

on Materials Analysis, April 2005. 305 SWGDRUG, 2011, op.cit., Recommendation 2.3(a).
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interpretations for their findings, where appropriate; making clear the strengths and any 

limitations in their advice or evidence; [and] declaring anything that might undermine the 

integrity of their evidence or its use ... .”306

5.3.5 Verification and Consultation 

If the examiner followed the ACE-V process, the report should disclose or refer the reader to the 

record of who verified the results, when verification occurred, and what information the 

verifying examiner had about the previous comparisons. If the Verification phase involved a 

difference of opinion, then the existence of the disagreement should be noted in the report and 

the basis for the final consensus should be stated in the report or other documentation.307

In some cases, an examiner seeks guidance from another expert (examiner or supervisor) before 

reaching a conclusion. Consultation is a way of sharing expertise and does not mean that there is 

a conflict. A poor quality unknown print, a poor quality known print, an irregular substrate, 

excessive deposition or lateral pressure, limited Level 2 Detail (see Chapters 3), and other factors 

could lead an examiner to consult with others. A conflict occurs when an examiner does not 

agree with another examiner during the verification, technical review, or administrative review. 

Such a disagreement is resolved in discussions among examiners who initially reached different 

conclusions or with the involvement of supervisory personnel up to the level of the laboratory 

director, if necessary. The recommendation for disclosure applies to conflicts rather than 

consultations.

5.3.6 Context 

Chapters 1 and 3 discuss the potentially biasing effects of contextual information. As those 

chapters explained, observers’ expectations have been shown to influence judgment in a broad 

range of tasks. Because “the possibility of biases influencing the decision making process of 

examiners” cannot be dismissed,308 a report should reveal the context of the examination by 

describing or referring the reader to the information about the case that an examiner received. 

For example, the possibility of an expectancy effect in comparing and evaluating a pair of prints 

argues in favor of revealing whether an examiner was informed that the exemplars were for 

elimination purposes, that they came from suspects in the case, or that they were the result of an 

AFIS search.309 

Chapter 3 observes that in some laboratories, examiners are exposed to a great deal of 

information that is clearly not related to or necessary for their analysis and calls upon 

laboratories to minimize the amount of extraneous, domain-irrelevant information that is 

 

306 SWGDRUG, 2004, op. cit., Recommendation 2.3.1.

307 Compare SWGFAST, 2010, op. cit., Standard 5.

308 SWGFAST, 2009, op. cit. 309 Dror, I. and J. Mnookin. “The Use of Technology in Human Expert Domains: Challenges and Risks Arising 

From the Use of Automated Fingerprint Identification Systems in Forensic Science.” Law, Probability & Risk, 9 

(2010): 47 – 67. An additional reason to document the fact of an AFIS search arises when candidates from this 

search are excluded. These exclusions increase the probative value of a match to a suspect. Aitken, C. and F. Taroni. 

Statistics and the Evaluation of Evidence for Forensic Scientists. 2nd ed. John Wiley & Sons, 2004; Kaye, D. 

“Rounding Up the Usual Suspects: A Legal and Logical Analysis of DNA Database Trawls.” North Carolina Law 

Review, 87, no. 2 (2009): 425 – 503. For a modest number of exclusions, however, the effect is small.
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provided to examiners. The recommendation here complements this suggestion by asking for 

disclosure of the information actually provided to examiners. This does not mean that the 

examiner must write out everything that is known about the background of the case. For 

example, if an examiner was exposed to a police case file or report containing information about 

the suspect’s criminal record or the suspect’s admissions to the police, the report could simply 

note that the examiner read the police report that contained information about the suspect before 

reaching a conclusion. 

5.3.7 References to Other Documentation

The report itself should at least describe the highlights of the examination of the evidence, and it 

should be an “accurate summary of significant material contained in the case notes.”310 But it 

need not present every detail of the process. If documentation, such as bench notes or additional 

images, is not appended to the report, the report should note that these materials are on file and 

can be obtained from the laboratory upon request.311 

For example, if more than one examiner reached a conclusion about the sufficiency or similarity 

of two images, the conclusions should be recorded in the documentation and noted in the 

summary report. The quality assurance and quality control measures in place also should be 

noted. Because these measures would be spelled out in written protocols and statements of 

standard operating procedures, it should be sufficient to refer to these documents. 

The Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) 

suggests that “the substrate, development medium, or preservation method can have a significant 

impact on the appearance of a latent print” and that “additional analytical factors, particularly on 

complex prints, provide the basis for distortion interpretation and explanations for variation in 

appearance.”312 Consequently, the documentation should record information about the substrate, 

development medium, and preservation method (e.g., lift, photograph, or legible copy).

The results of the effort to develop prints also should be documented by annotated images or 

written descriptions that record how many and which prints were determined to be suitable for 

comparison as well as the existence of prints determined to be unsuitable for comparison.313 If 

the latent print examiner uses enhancement technology, he or she should retain the unenhanced 

image and maintain an audit trail of all digital enhancements to subsequent copies (see Chapter 

4). The FBI laboratory suggests that 

once the evidence has been received in the Latent Print Unit for processing, case 

note documentation should chronologically include each activity and the results of 

the activity. Documentation should include any development techniques applied, 

the date the process was applied, and the result. The documented result should 

include the presence or absence of any prints and the indication of whether the 

developed prints are suitable for capture either through scanning or photography. 

 

310 ASCLD, op. cit., p. 43. 311 See European Network, op. cit., Standard I1(f). 312 SWGFAST, 2010, op. cit., p. 2.

313 Compare ibid., Standard 1.1.2.
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This documentation process should continue until all processing techniques have 

been applied or the processing is discontinued.314

Furthermore, it recommends that 

case documentation should indicate the number of latent prints of value detected 

on each item, along with a description of the item, and which items did not 

contain any latent prints or latent prints of value. Additional requirements include 

the disposition of any images containing latent prints of value and any images of 

latent prints that were not analyzed, compared, or evaluated.315

SWGFAST suggests that “documentation ... may be accomplished by making a ‘no value’ 

notation (e.g., ‘NV’) on a lift, photograph, or legible copy retained as part of the case record [or] 

by indicating in case notes that ‘no value’ impressions are present on a lift or photograph.”316

Although SWGFAST adds that “copies of latent prints that are of no value do not need to be 

retained in the case record,” this Working Group recommends retaining all images for possible 

later review. 

Finally, the report or associated documentation should record the features that the examiner(s) 

considered and relied on in reaching a conclusion of identification, including those features used 

in any verification. All comparisons conducted during the course of the examination, including 

latent to exemplar, latent to latent, and exemplar to exemplar, should be documented. In some 

cases, a number of exclusions may be made. For example, an AFIS search will generate a list of 

candidates. When, in screening these candidates, exemplars are readily excluded, the 

documentation need not show the specific feature or features used for the exclusion, but the 

exemplars should be retained or be kept retrievable.317

The report or supporting documentation should explain, through annotations on images or in 

some other fashion, the features of the unknown that were selected for analysis and used for 

comparison.318 An apparent dissimilarity that is attributed to distortion or another cause should 

be noted.319 Providing this information complies with the International Organization for 

Standardization’s ISO/IEC 17025: 2005, clause 5.10.5,320 which requires that “the laboratory 

shall document the basis upon which the opinions and interpretations have been made” and 

responds to the concern that examiners might fail “to document which features within a latent 

print support their reasoning and conclusions.”321 A verifying examiner’s notes or other 

materials should document the verification in similar detail.

As discussed in Chapter 3, contemporaneous documentation of each major step in the 

examination process can help ensure the examination is conducted properly and thus reduce the 

 

314 Peterson, Dreyfus, Gische, et al., op. cit.

315 Ibid. 316 SWGFAST, 2010, op. cit., p. 3. 317 Ibid., Standard 2.4.

318 Ibid., Preamble. See also Chapter 3.

319 Compare SWGFAST, 2010, op. cit., p. 2. 320 International Organization for Standardization. General Requirements for the Competence of Testing and 

Calibration Laboratories, ISO/IEC 17025:2005(E), 2d ed. International Organization for Standardization, 2005.

321 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 143.
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100 

chance of error. It also can provide a record that might be useful for testimony by the examiner 

or other possible expert witnesses at a later time.

5.3.8 Definition of Terms

A report should define important technical terms, either explicitly or by reference to an 

authoritative, readily available source. For example, latent print examiners often refer to 

“individualization” as “identification,”322 but in ordinary parlance, an identification need not be 

an assertion that only one person on Earth could be the source of an impression. An eyewitness 

description might be used to “identify” a suspect, even though the individual so identified would 

not be the only person in the world to fit the description. Even the word “individualize” is not 

self-defining. It might mean that in a closed group of, say, seven suspects, only one suspect’s 

finger could be the source of a latent print, or it might represent a more powerful assertion that 

no other finger that has ever been or ever will be in existence can produce so similar a latent 

print. An explicit definition informs the reader of the intended meaning, and Chapter 1 discusses 

ways to define terms relating to the process of establishing an association between a known 

individual and a latent print. The importance of defining terms clearly is widely recognized in the 

forensic sciences,323 and this part of the recommendation also follows from Recommendation 5.1 

on making the report understandable to lay readers. 

Recommendation 5.2: A report should: 

a. Identify the latent print examiner(s); 

b. Describe the items submitted to the examiner(s); 

c. List the procedures used by the examiner to develop, visualize, or enhance the 

friction ridge impressions; 

d. List all comparisons conducted; 

e. State all conclusions with the method used to reach them; 

f. Note any important limitations to the conclusions; 

g. Indicate whether a verification was made and whether there was any conflict of 

opinion among examiners prior to the reported conclusions; 

h. Note (or refer to external documentation of) any information about the case that 

the examiner(s) received; 

i. Note the existence of additional documentation; and 

j. Define important technical terms, either explicitly or by reference to an 

authoritative, readily available source. 

 

322 E.g., SWGFAST, 2003, op. cit., Standard 1. A draft of the document intended to replace these standards does not 

use the word “identification.” Scientific Working Group on Friction Ridge Analysis, Study and Technology. Draft 

for Comment: Standards for Examining Friction Ridge Impressions and Resulting Conclusions (To Replace: 

Friction Ridge Examination Methodology for Latent Print Examiners, Version 1.01, and Standards for Conclusions, 

Version 1.0). Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, August 

2010, p. 4. Another draft document, the Scientific Working Group on Friction Ridge Analysis, Study and 

Technology. Standard Terminology of Friction Ridge Examination (To Replace: Glossary, Version 2.0). Version 3.

Scientific Working Group on Friction Ridge Analysis, Study and Technology, February 11, 2011, lists 

“individualization” as the primary meaning of “identification.”

323 For example, European Network, op. cit., Activity I. SWGDRUG, 2004, op. cit., Recommendation 3.2.1.
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5.4 Summary

A report and documentation that contain the information listed in these recommendations 

provide an accessible record of the work of latent print examiners. The level of detail is 

sufficient to inform investigators, prosecutors, defense counsel, other experts, and judges or 

juries as to how the analysis was conducted and what conclusions were reached. This type of 

reporting meets scientific norms, quality assurance, and legal concerns. Appendices offer sample 

language for a full report, a shortened report with minimal requirements, and a report with 

qualified conclusions. 
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102 

Appendix 5-A: Sample Report Summary

 

Bureau of Investigation 123 Main Street 

Laboratory Division, Latent Print Section Washington, D.C. 20035 

SAMPLE REPORT OF EXAMINATION

To: BI Agent John Dunne Date: October 20, 2011 

Los Angeles Field Office

Case Number: LA-123456 

Case Title: Bank of Los Angeles 

 123 California Blvd. 

 Los Angeles, CA 

 Aug. 28, 2011 

 Bank Robbery 

Date specimens received: September 3, 2011 

Fingerprint Analyst: Susanne Brown 

The items listed below were examined in the Latent Print Section. 

Item # Description

1 Demand note beginning, “I have a gun...”

2 Bank of Los Angeles withdrawal form

3 Pen with chain 

4 Lift indicated as coming from customer 

counter

Table 1: Items examined in Latent Print Section 

Results of Examinations 

Items of evidence submitted to the Latent Print Section for examination may be examined 

visually, examined with various light sources, or processed with chemicals and powders to detect 

the presence of latent friction ridge prints. The specific sequence of examinations and processes 

depends upon the nature of the evidence.1

 

1 See Bureau of Investigation, Processing Guide for Developing Latent Prints, Revised 2001.

 I applied the following processes to the submitted 

items as follows:
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Item 

# Description Processing techniques

1 Demand note beginning, “I have a gun...” Visual, LASER, ultraviolet, 

Crimescope, 1,8-Diazafluoren-9-

one/LASER, Ninhydrin, Physical 

Developer

2 Bank of Los Angeles withdrawal form Visual, LASER, ultraviolet, 

Crimescope, 1,8-Diazafluoren-9-

one/LASER, Ninhydrin, Physical 

Developer

3 Pen with chain Visual, LASER, ultraviolet, 

Crimescope, Cyanoacrylate Fuming, 

reflective ultraviolet imaging system, 

Cyanoacrylate Dye 

Stain/LASER/ultraviolet/Crimescope, 

White Powder 

4 Lift indicated as coming from customer 

counter

Visual—see crime scene log for 

additional information

Table 2: Processing techniques applied to submitted items 

BI conducts friction ridge print examinations using the Analysis, Comparison, Evaluation, and 

Verification (ACE-V) process. The first phase in the process is Analysis, which is conducted 

independently on first the latent then the known prints. During this phase, each print is analyzed 

for both the quality and quantity of information present. The qualitative assessment is based 

upon the clarity of the friction ridges, the substrate on which the latent print was developed, 

deposition and lateral pressures, and the processing techniques applied. The quantitative analysis 

takes into account all of the information present in the print, broken down into three levels of 

detail. Level 1 Detail consists of the overall ridge flow, including pattern type and orientation of 

the print based upon that ridge flow. Level 2 Detail lies in individual ridge paths, including those 

of continuous ridges as well as ridges that come to an end, divide to form two or more ridges, or 

appear as isolated dots. Analysis of these ridge characteristics accounts for their type, direction, 

location, and spatial sequence. Level 3 Detail includes individual ridge attributes, particularly 

shape and width along the length of each ridge. The quality and quantity of information observed 

during the Analysis phase determines whether the print contains suitable information to conduct 

a comparison with another print. 

Results of Analysis 

I detected four latent fingerprints on Items 1, 2, and 4 that were suitable for comparison:
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Chapter 5: Reports and Documentation 

104 

Item 

# Description # of prints Processing technique

1 Demand note beginning, “I have a gun...” 2 1 1,8-Diazafluoren-9-

one/LASER, 1 Ninhydrin 

2 Bank of Los Angeles withdrawal form 1 Ninhydrin

4 Lift indicated as coming from customer 

counter 

1 Black powder lift

Table 3: Prints determined to be suitable for comparison and the processing technique used to 

detect them

In the Comparison phase of the ACE-V process, I conducted a side-by-side comparison of a 

latent print with an exemplar. I examined both prints for similarities and differences, assessing 

ridges sequentially for agreement or disagreement in all levels of detail.

In the Evaluation phase of the ACE-V, I considered all of the information gathered during 

Analysis and Comparison to reach conclusions about the origin of the latent prints. I made 

identifications as well as exclusions. An exclusion is an opinion that the two prints did not 

originate from the same source because there is information in disagreement in the comparable 

areas of the two prints that would not be present if the prints came from the same finger. An 

identification is an opinion that the two prints originated from the same source because the 

information in the comparable areas of two prints is in sufficient agreement. An identification 

does not necessarily eliminate the possibility that another person in the world could leave a print 

with areas of similar agreement. It means that within the examiner’s experience and knowledge, 

no other prints with this much similarity have come from different people. 

Results of Comparison and Evaluation 

After a conversation with the case agent (see Table 7), I compared the four latent fingerprints to 

the fingerprints of THOMAS SMITH, BI #123456, with the following results:

Item 

# Description # of prints

Results of comparison with 

THOMAS SMITH, BI 

#123456

1 Demand note beginning, “I have a gun...” 2 2 Identifications

2 Bank of Los Angeles withdrawal form 1 Exclusion

4 Lift indicated as coming from customer 

counter 

1 Exclusion

Table 4: Results of comparisons with THOMAS SMITH, BI #123456 

The remaining two unidentified latent fingerprints were searched in the BI automated fingerprint 

identification system (AFIS). I reviewed the resulting list of candidates (available upon request 

to the BI) and reached the following conclusions:
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Chapter 5: Reports and Documentation 

105 

Item 

# Description # of prints Results of AFIS search

2 Bank of Los Angeles withdrawal form 1 No Identification effected

4 Lift indicated as coming from customer 

counter

1 Identification with JANE 

JONES, BI #987654

Table 5: Results of AFIS searches 

The remaining unidentified latent fingerprint (on item #2) is not a fingerprint of JANE JONES, 

BI #987654. 

Summary of Evaluation 

Item 

# Description # of prints Evaluation Summary

1 Demand note beginning, “I have a gun...” 2 2 Identifications with

THOMAS SMITH, BI 

#123456

2 Bank of Los Angeles withdrawal form 1 Not a fingerprint of 

THOMAS SMITH, BI 

#123456, or JANE JONES, 

BI #987654

4 Lift indicated as coming from customer 

counter

1 Identification with JANE 

JONES, BI #987654

Table 6: Summary of evaluation 

The presence of a friction ridge print on an item of evidence indicates contact was made between 

the source and the item of evidence. The presence of a friction ridge print alone does not 

necessarily indicate the significance of either the contact or the time frame during which the 

contact occurred.

Due to the many factors involved in the deposition of a friction ridge print, neither the absence of 

a friction ridge print on evidence nor the exclusion of a friction ridge print with a given source 

necessarily precludes that source from having touched the evidence. 

Results of Verifications and Blind Verifications

The Verification phase of the ACE-V process consists of the application of the Analysis, 

Comparison, and Evaluation phases of the ACE-V process to a friction ridge print by another 

qualified examiner who then expresses his or her agreement or disagreement with the original 

examiner’s conclusion. On October 18, 2011, Fingerprint Analyst Robert Johnson, knowing the 

outcome of the original examination, verified the identifications. There were no conflicts of 

opinion. 

On October 19, 2011, Fingerprint Analyst James Bishop conducted a blind verification of the 

identification with JANE JONES. (In blind verifications, the verifying examiner is unaware of 

the original examiner’s conclusion.) A conflict of opinion occurred during this blind verification 

of the identification with JANE JONES. Initially, the verifier deemed the comparison 
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Chapter 5: Reports and Documentation 

106 

inconclusive due to poor quality exemplars. Upon consultation with the primary analyst, the 

blind verifier realized that he had not received all available exemplars. After comparing the 

additional exemplars, the verifier concurred with the identification decision. 

Additional documentation, including bench notes and annotated images of the latent prints for 

both the primary analyst and verifiers, is retained as part of the case record and can be provided 

upon request. The BI Laboratory Division’s Quality Assurance Manual and Standard Operating 

Procedures can be found online at www.BI.org. 

Case Information Received by the Fingerprint Analyst

The following table summarizes the case-related information that I received for this case:

Date Communication 

Type Description 

September 3, 

2011 

Incoming letter Letter from contributor submitted with the 

evidence. Details of case, including type of crime, 

location of crime, date of crime, description of how 

bank robbery occurred, and description of evidence 

being submitted were included in the letter. No 

individuals to compare were provided. 

September 14, 

2011 

Telephone call 

(documented on 

Activity & 

Communication 

Log)

Telephone call with Case Agent naming individual 

to compare. THOMAS SMITH, BI #123456, had 

been developed as a suspect due to information 

from a confidential informant. 

Table 7: Information on case received by examiner 

For questions about the content of this report, please contact Fingerprint Analyst Susanne Brown

at (202) 123-4567. 

The specimens are being returned under separate cover.

 Susanne Brown 

 Fingerprint Analyst 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 5: Reports and Documentation 

107 

Appendix 5-B: Sample Report Summary, Short Version

 

Bureau of Investigation 123 Main Street 

Laboratory Division, Latent Print Section Washington, D.C. 20035 

SAMPLE REPORT OF EXAMINATION

To: BI Agent John Dunne Date: October 20, 2011 

Los Angeles Field Office

Case Number: LA-123456 

Case Title: Bank of Los Angeles 

 123 California Blvd. 

 Los Angeles, CA 

 Aug. 28, 2011 

 Bank Robbery 

Date specimens received: September 3, 2011 

Fingerprint Analyst: Susanne Brown 

The items listed below were examined in the Latent Print Section. 

Item # Description

1 Demand note beginning, “I have a gun...”

2 Bank of Los Angeles withdrawal form

3 Pen with chain 

4 Lift indicated as coming from customer 

counter 

Table 1: Items examined in Latent Print Section 

Items of evidence submitted to the Latent Print Section for examination may be examined 

visually, examined with various light sources, or processed with chemicals and powders to detect 

the presence of latent friction ridge prints. The specific sequence of examinations and processes 

depends upon the nature of the evidence.1

 

1 See Bureau of Investigation, Processing Guide for Developing Latent Prints, Revised 2001.

A complete list of the processes used in this 

submission is maintained in the case record and can be furnished upon request. 
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Chapter 5: Reports and Documentation 

108 

Results of Examinations

Four latent fingerprints were detected on the items and compared to THOMAS SMITH, BI 

#123456, with the following results: 

Item 

# Description # of prints

Results of comparison with 

THOMAS SMITH, BI 

#123456

1 Demand note beginning, “I have a gun...” 2 2 Identifications

2 Bank of Los Angeles withdrawal form 1 1 Exclusion

3 Pen with chain 0 N/A

4 Lift indicated as coming from customer 

counter

1 1 Exclusion

Table 2: Results of comparisons with THOMAS SMITH, BI #123456 

The remaining unidentified latent fingerprints were searched in the BI automated fingerprint 

identification system (AFIS) with the following results:

Item 

# Description # of prints Results of AFIS search

2 Bank of Los Angeles withdrawal form 1 No Identification effected

4 Lift indicated as coming from customer 

counter 

1 1 Identification with JANE 

JONES, BI #987654 

Table 3: Results of AFIS searches 

The remaining unidentified latent fingerprint (on item #2) is not a fingerprint of JANE JONES, 

BI #987654. 

Friction ridge print examinations are conducted using the Analysis, Comparison, Evaluation, and 

Verification (ACE-V) process. The steps of ACE-V are applied to each examination as 

appropriate. Analysis is the assessment of the quantity and quality of the information present in 

the print to determine if sufficient reliable details are present to conduct a comparison with 

another print. Comparison is the side-by-side observation of friction ridge prints to determine 

whether or not the information in two prints is in agreement. Evaluation is the formulation of a 

conclusion based upon the information gathered during analysis and comparison. The evaluation 

can result in an exclusion, an identification, or an inconclusive outcome. An exclusion is an 

opinion that the two prints did not originate from the same source because there is information in 

disagreement in the comparable areas of two prints that would not be present if the prints came 

from the same finger. An identification is an opinion that the two prints originated from the same 

source because the information in the comparable areas of two prints is in sufficient agreement. 

An identification does not necessarily eliminate the possibility another person in the world could 

leave a print with areas of similar agreement. It means that within the examiner’s experience and 

knowledge, no other prints with this much similarity have come from different people. 

Verification is the independent application of the Analysis, Comparison, and Evaluation phases 

of the ACE-V process to a friction ridge print by another examiner. 
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The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 5: Reports and Documentation 

109 

The presence of a friction ridge print on an item of evidence indicates that contact was made 

between the source and the item of evidence. The presence of a friction ridge print alone does not 

necessarily indicate the significance of the contact or the time frame during which the contact 

occurred.

Due to the many factors involved in the deposition of a friction ridge print, neither the absence of 

a friction ridge print on evidence nor the exclusion of a friction ridge print with a given source 

necessarily precludes that source from having touched the evidence. 

Verifications of the identifications were conducted by Fingerprint Analyst Robert Johnson, 

knowing the outcome of the original examination, on October 18, 2011. There were no conflicts 

of opinion. 

On October 19, 2011, Fingerprint Analyst James Bishop conducted a blind verification of the 

identification with JANE JONES. (In blind verifications, the verifying examiner is unaware of 

the original examiner’s conclusion.) A conflict of opinion occurred during this blind verification 

of the identification with JANE JONES. Initially, the verifier deemed the comparison 

inconclusive due to poor quality exemplars. Upon consultation with the primary analyst, the 

blind verifier realized that he had not received all available exemplars. After comparing the 

additional exemplars, the verifier concurred with the identification decision. 

Additional documentation, including bench notes, annotated images of the latent prints for both 

the primary analyst and verifier, and communications indicating the case information received by 

the analyst and the date on which that information was received are retained as part of the case 

record and can be provided upon request. The BI Laboratory Division’s Quality Assurance 

Manual and Standard Operating Procedures can be found online at www.BI.org. 

For questions about the content of this report, please contact Fingerprint Analyst Susanne Brown

at (202) 123-4567. 

The specimens are being returned under separate cover.

 Susanne Brown

 Fingerprint Analyst 
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 5: Reports and Documentation 

110 

Appendix 5-C: Sample Report Summary with Qualified Conclusions

Bureau of Investigation 123 Main Street 

Laboratory Division, Latent Print Section Washington, D.C. 20035 

SAMPLE REPORT OF EXAMINATION

To: BI Agent John Dunne Date: October 20, 2011 

Los Angeles Field Office

Case Number: LA-123456 

Case Title: Bank of Los Angeles 

 123 California Blvd. 

 Los Angeles, CA 

 Aug. 28, 2011 

 Bank Robbery 

Date specimens received: September 3, 2011 

Fingerprint Analyst: Susanne Brown 

The items listed below were examined in the Latent Print Section:

Item # Description

1 Demand note beginning, “I have a gun...”

2 Bank of Los Angeles withdrawal form

3 Pen with chain 

4 Lift indicated as coming from customer 

counter

Table 1: Items examined in Latent Print Section 

Items of evidence submitted to the Latent Print Section for examination may be examined 

visually, examined with various light sources, or processed with chemicals and powders to detect 

the presence of latent friction ridge prints. The specific sequence of examinations and processes 

depends upon the nature of the evidence.1

 

1 See Bureau of Investigation, Processing Guide for Developing Latent Prints, Revised 2001.

 A complete listing of the processes used in this 

submission is maintained in the case record and can be furnished upon request. 
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The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 5: Reports and Documentation 

111 

Results of Examinations 

Friction ridge print examinations are conducted using the Analysis, Comparison, Evaluation, and 

Verification (ACE-V) process. Analysis is the assessment of the quantity and quality of the 

information present in the print to determine if sufficient reliable details are present to conduct a 

comparison with another print. Comparison is the side-by-side observation of friction ridge 

prints to determine the extent to which the information in two prints is in agreement. Evaluation 

is the formulation of an opinion on the degree to which the information gathered during analysis 

and comparison supports the hypothesis (S) of a common source for the exemplar and the latent 

print or instead supports the hypothesis (D) that the exemplar and the latent come from different 

individuals. An opinion of strong support for S does not necessarily eliminate the possibility 

another person in the world could leave a print with areas of similar agreement. It means that 

within the examiner’s experience and knowledge, prints from the same finger would be expected 

to display this much similarity, whereas prints from different fingers would not be. Verification 

is the independent application of the Analysis, Comparison, and Evaluation phases of the ACE-V 

process to a friction ridge print by another examiner. 

Four latent fingerprints were detected on the items and compared to exemplar prints from 

THOMAS SMITH, BI #123456, to provide evidence for or against the hypothesis that Thomas 

Smith is the source of the latent fingerprints. 

Item 

# Description # of prints

Results of comparison with 

THOMAS SMITH, BI 

#123456

1 Demand note beginning, “I have a gun...” 2 Strong support for S

2 Bank of Los Angeles withdrawal form 1 Strong support for D

3 Pen with chain 0 N/A

4 Lift indicated as coming from customer 

counter

1 Strong support for D

Table 2: Results of comparisons with THOMAS SMITH, BI #123456 

The remaining unidentified latent fingerprints were searched in the BI automated fingerprint 

identification system (AFIS) with the following results:

Item 

# Description # of prints Results of AFIS search

2 Bank of Los Angeles withdrawal form 1 No support for any candidate as 

the source 

4 Lift indicated as coming from customer 

counter 

1 Strong support for JANE 

JONES, BI #987654 as the 

source

Table 3: Results of AFIS searches 

The remaining unidentified latent fingerprint (on item #2) is very different from the exemplar 

from JANE JONES, BI #987654 and provides strong support for the hypothesis that she is not its 

source. 
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Chapter 5: Reports and Documentation 

112 

The presence of a friction ridge print on an item of evidence indicates contact was made between 

the source and the item of evidence. The presence of a friction ridge print alone does not 

necessarily indicate the significance of the contact or the time frame during which the contact 

occurred.

Due to the many factors involved in the deposition of a friction ridge print, neither the absence of 

a friction ridge print on evidence nor the absence of a friction ridge print consistent with a given 

source necessarily precludes that source from having touched the evidence. 

Blind verifications of all results were conducted by Fingerprint Analyst Robert Johnson on 

October 18, 2011. There were no conflicts of opinion. 

Additional documentation, including bench notes, annotated images of the latent prints for both 

the primary analyst and verifier, and communications indicating the case information received by 

the analyst and the date on which that information was received are retained as part of the case 

record and can be provided upon request. The BI Laboratory Division’s Quality Assurance 

Manual and Standard Operating Procedures can be found online at www.BI.org. 

For questions about the content of this report, please contact Fingerprint Analyst Susanne Brown

at (202) 123-4567. 

The specimens are being returned under separate cover.

 Susanne Brown

 Fingerprint Analyst
Latent Print Examination and Human Factors: Improving the Practice through a Systems Approach

The Report of the Expert Working Group on Human Factors in Latent Print Analysis

Chapter 6: Testimony

113 

Chapter 6: Testimony

Introduction and Scope

Latent print examinations are conducted not merely to assist criminal investigators but also to 

produce legally admissible evidence that can exonerate or implicate defendants. Fingerprint 

evidence has been used in American courts since 1910.327 Other pattern and impression evidence 

also has a venerable history.

328 In recent years, however, forensic science testimony associating 

marks or impressions with specific sources has come under intense scrutiny—first, in the 

academic literature,329 then in the courtroom,330 and again in the 2009 National Research Council 

(NRC) report.331 

Testifying is a quintessentially human activity, and latent print testimony is the product of a long 

series of actions in which human factors issues are prominent. Previous chapters focus on the 

pretrial stages of the production of latent print evidence. They examine the role of human 

perception and cognition in the production of this evidence and ways to maintain or improve the 

quality of the resulting evidence. This chapter concentrates on the interactions of latent print 

examiners with other participants in the criminal justice system at and shortly before trial. 

Human limitations and dispositions are as important in this phase of latent print examination 

work as they are in earlier phases. Developing and implementing procedures and practices that 

encourage experts to communicate their findings accurately and fairly to lawyers, judges, and 

juries and to detect and correct errors in this process is a crucial component of a system that 

reduces the opportunities for errors in the production and presentation of courtroom fingerprint 

evidence.332

This chapter therefore discusses pretrial communications between experts and lawyers and 

makes recommendations about preparation for trial and the information that experts should 

communicate to judges and juries. Although the discussion is confined to presenting the results 

of examinations of friction skin impressions for the purpose of associating latents (anonymous, 

 

327 Mnookin, J. “Fingerprint Evidence in an Age of DNA Profiling.” Brooklyn Law Review, 67 (2001): 13.

328 Thomas, F. “Comments on the Discovery of Striation Matching and on early contributions to Forensic Firearms 

Identification.” Journal of Forensic Science, 12 (1967): 1 – 7.

329 E.g., Faigman, D., D. Kaye, M. Saks, et al. Modern Scientific Evidence: The Law and Science of Expert 

Testimony. 1st ed. West Publishing Company, 1997. 330 For discussions of the cases, see McCormick, C. McCormick on Evidence. Edited by Kenneth Broun. 6th ed. 

Thomson/West, 2006; Giannelli, P. and E. Imwinkelried. Scientific Evidence. 4th ed. Matthew Bender, 2007, Ch. 

18A; Faigman, Kaye, Saks, et al., op. cit.

331 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009, pp. 102–106.

332 The Working Group was asked to examine “the role of human factors and their contributions to errors in latent 

print analysis.” Clearly, “analysis” does not end with the Analysis phase of the Analysis, Examination, Comparison, 

and Verification (ACE-V) process. Nor, in the view of a substantial majority of the Working Group, does it end 

when a laboratory examination is completed and a report is signed. “Errors in latent print analysis” as evidence in 

legal proceedings can occur because of the manner in which this evidence is presented. Truncating the inquiry into 

the work of latent print examiners at the production of a written report would produce an incomplete review of the 

full process by which latent print evidence emerges from a crime scene and reaches the legal decision makers, at 

least in cases that go to trial.
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unknown prints) with exemplars (identified, known prints) in criminal trials, and differences 

between the civil and criminal rules of discovery are not considered, much of the discussion also 

applies to civil cases involving private parties.

Sections 6.1 through 6.5 describe various aspects and functions of expert testimony as well as 

some of the most pertinent legal doctrines. Section 6.6 discusses the admissibility and 

desirability of different types of testimony about the possibility that an examiner’s finding that 

the items are (or are not) associated with one another is incorrect. Section 6.7 describes a 

spectrum of conceivable modes of conveying expert knowledge and findings about the possible 

association between a friction skin impression and its source. Finally, section 6.8 discusses 

quality assurance and quality control for testimony.

To situate testimony about identifications based upon the features of friction ridge skin within 

the broader range of forensic identification testimony, the discussion is not confined to the 

Analysis, Comparison, Evaluation, and Verification (ACE-V) process as currently practiced. As 

noted in earlier chapters, categorical conclusions within ACE-V are not the only way to make 

and communicate inferences from the comparison of latent prints and exemplars. In other areas 

of forensic science that investigate the possible association between known and unknown 

samples, witnesses present their findings differently, and one cannot simply assume that what is 

most familiar in one field is the only way to convey expert knowledge in the courtroom. This

chapter therefore surveys a broad range of testimony that, at least in principle, might be provided 

at trial. At one pole, an expert might merely inform the judge or jury of the similarities or 

dissimilarities in the features of a pair of prints and not draw any inferences from these data. At 

the other pole, when the similarity is extensive, the expert might attribute the latent print to a 

specific finger (source attribution). In between these poles lie various other forms of qualitative 

or quantitative testimony. The Working Group reached no consensus on which one of the various 

alternative modes of presentation is best warranted by existing scientific research findings and 

other empirical knowledge. Neither does the Group purport to describe which form of testimony 

best satisfies the needs of the legal system. But for the reasons given in Chapter 3, the Working 

Group agrees that if source attributions are made, they should not be “to the exclusion of all 

others in the world” (Recommendation 3.7). 

With respect to latent prints, two major concerns relevant to testimony are statements about error 

rates and individualization. This chapter does not attempt to settle the arguments among forensic 

scientists, psychologists, statisticians, legal scholars, and latent print examiners on fingerprint 

individualization and the risks of erroneous identifications or exclusions.333 Instead, it seeks to 

place fingerprint identification testimony in a broader context and to consider whether more 

modest claims of association and statements about errors would meet the law’s purposes without 

compromising the integrity of latent print examiners and without discarding important 

information. 

 

333 For some assessments, see Champod, C. “Fingerprint Examination: Towards More Transparency.” Law, 

Probability & Risk, 7 (2008): 111; Mnookin, J. “The Validity of Latent Fingerprint Identification: Confessions of a 

Fingerprinting Moderate.” Law, Probability & Risk, 7 (2008): 127. 
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6.1 Purpose, Form, and Preparation of Expert Testimony

Expert witnesses use or impart specialized knowledge and information generally unknown to the 

jury or judge to “assist the trier of fact to understand the evidence or to determine a fact in issue 

... .”334 Expert testimony need not be delivered in the form of an opinion. Expert witnesses also 

can act as teachers, educating fact finders about pertinent principles or findings in their 

disciplines. For example, a latent print expert might explain why prints would not be found on a 

particular surface without offering a personal opinion on the reason for their absence in a 

particular case.

During a trial, counsel’s questioning frames the expert’s presentation. The expert may not simply 

decide what information to discuss but must answer counsel’s questions. This can create some 

tension between the goal of being complete and the need to be responsive. In resolving this 

tension, “ethical considerations and professional standards properly place a number of 

constraints on the expert’s behavior.”335 One such constraint is “a requirement of candor. While 

an expert is ordinarily under no legal obligation to volunteer information, professional ethics 

may compel this ... when the expert believes that withholding information will change 

dramatically the picture that his ... analyses, properly understood, convey.”336 Thus, the “guiding 

principles” proposed by the American Society of Crime Laboratory Directors/Laboratory 

Accreditation Board (ASCLD/LAB) advise forensic scientists to “attempt to qualify their 

responses while testifying when asked a question with the requirement that a simple ‘yes’ or ‘no’ 

answer be given, if answering ‘yes’ or ‘no’ would be misleading to the judge or the jury.”337

Pretrial preparation with the attorney who will be calling the expert is essential to effective trial

presentation. Preparation includes educating the lawyer, who should understand the evidence 

involved, appreciating the limitations of the discipline and the forensic findings, and recognizing 

any exculpatory or qualifying information that must be disclosed. Lawyers should not present the 

testimony of examiners without first conferring about the expert’s report and anticipated 

testimony, including the use of visual aids.338

Recommendation 6.1: The trial preparation process should address the presentation of 

technical information in lay terms, the organization of the direct examination, possible 

cross-examination, and the possible use of visual aids.

 

334 Federal Rules of Evidence 702. In full, the rule states that:

If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence 

or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or 

education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon 

sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the 

witness has applied the principles and methods reliably to the facts of the case.

For more extensive discussions of expert testimony, see, for example, Faigman, Kaye, Saks, et al., op. cit.; Giannelli 

and Imwinkelried, op. cit.; Kaye, D., D. Bernstein, and J. Mnookin. The New Wigmore, A Treatise on Evidence: 

Expert Evidence. 2nd ed. Aspen Publishers, 2011; McCormick, op. cit. 335 Feinberg, S., ed. The Evolving Role of Statistical Assessments as Evidence in the Courts. Springer, 1989, p. 161. 336 Ibid. 337 American Society of Crime Laboratory Directors/Laboratory Accreditation Board. ASCLD/LAB Guiding 

Principles of Professional Responsibility for Crime Laboratories and Forensic Scientists. Version 1.1. 2009, 

Principle 19.

338 Using pictures of prints not involved in the case should not be necessary and may be objectionable under the 

rules of relevance.
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6.2 Pretrial Discovery

There is no legal barrier to defense counsel contacting a prosecution expert to discuss the case.339

Of course, the mere fact that opposing counsel may contact an expert does not require the expert 

to cooperate, and there may be concerns about breaching the protection given to an attorney’s 

work product. However, openness may help ensure that opposing counsel understands the 

discipline, the evidence, and the opinion. It also enhances credibility if the expert on the witness 

stand discloses sharing information with opposing counsel. 

Different considerations apply to a criminal defense expert. Unless and until a defense expert is 

designated a testifying witness, this expert may be considered part of the defense team, and 

defense counsel needs to protect confidential communications that come from clients.340 Once 

designated as a witness, however, this expert should have the same status as a prosecution expert. 

6.3 Ethical and Professional Obligations

An expert witness who is a member of a learned profession has obligations to his profession as 

well as to his employer.341 More than 30 years ago, an NRC panel called on “professional 

organizations to develop standards for expert witnesses in legal proceedings ... .”342 More 

recently, the NRC committee on forensic science proposed “a national code of ethics for all 

forensic science disciplines” such that “those forensic scientists who commit serious ethical 

violations” could be sanctioned “through a certification process for forensic scientists.”343 It 

observed that 

many forensic science organizations—such as the American Academy of Forensic 

Sciences, the California Association of Criminalists, and ASCLD [American 

Society of Crime Laboratory Directors]—have codes of ethics or codes of 

professional practice imploring members to act with honesty, integrity, and 

objectivity; to work within the bounds of their professional competence; to 

present testimony and reports in a clear and objective manner; and to avoid 

conflicts of interest and potential bias, among other things.344

To avoid incomplete or one-sided presentations, ample disclosure of reasoning, limitations, and 

exculpatory material in pretrial reports, as discussed in section 6.1, is especially important, as is a 

shared professional ethic that is strong enough to resist pressure from lawyers who sometimes 

seek unduly oversimplified and exaggerated presentations of technical information. Thus, 

forensic scientists have urged that

 

339 Gross, S. “Expert Evidence.” Wisconsin Law Review, 1113 (1991): 1151. 340 United States v. Tharpe, 38 M.J. 8, 28 (C.M.A. 1993). 341 Feinberg, op. cit., pp. 161-62; Kaye, Bernstein, and Mnookin, op. cit., § 11.4(c); Lubet, S. “Expert Witnesses: 

Ethics and Professionalism.” Georgetown Journal of Legal Ethics, 12 (1999): 465. 342 Feinberg, op. cit., p. 162. 343 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 214.

344 Ibid. 
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all crime laboratories, both public and private, should have a code of 

ethics/conduct. These codes need to stress the best interests of society through 

government service and justice, government responsibility for professionalism 

and cost effectiveness, integrity (both professionally and regarding evidence), 

objectivity, staying within the bounds or limits of what the science can provide, 

maintaining confidentiality, complying to legal demands such as disclosure, and 

being truthful.345

In view of the status of experts who represent a learned and skilled profession and the latitude 

given to the form and bases of their testimony (see section 6.1), the Working Group 

recommends: 

Recommendation 6.2: Forensic service providers should adopt codes of ethics that 

require testifying in a nonpartisan manner; answering questions from both the 

prosecution and the defense directly, accurately, and fully; and providing appropriate 

scientific information before, during, and after trial.

This precept already is widely accepted in the forensic community. The Scientific Working 

Group on Friction Ridge Analysis, Study and Technology (SWGFAST) has a short aspirational 

code for friction ridge examiners that forbids knowing misrepresentations and specifies that 

“testimony shall be rendered in an impartial manner to promote the understanding of 

examinations and findings.”346 The guiding principles of ASCLD/LAB specifically state that 

“wording should not be such that inferences may be drawn which are not valid, or that slant the 

opinion to a particular direction.”347 As previously noted, to achieve impartial testimony, 

ASCLD/LAB also advises forensic scientists to “attempt to qualify their responses while 

testifying when asked a question with the requirement that a simple ‘yes’ or ‘no’ answer be 

given, if answering ‘yes’ or ‘no’ would be misleading to the judge or the jury.”348 The European 

Network of Forensic Science Institutes expects analysts to “deal with questions truthfully, 

impartially and flexibly in a language which is concise, unambiguous and admissible;” to “give 

explanations to specific questions in a manner that facilitates understanding by nonscientists;” to 

“consider additional information and alternative hypotheses that are presented to you;” to 

“consider and evaluate these and express relevant opinions taking into account the limitations on 

opinions which cannot be given without further examination and investigation;” and to “clearly 

differentiate between fact and opinion and ensure that the opinions you express are within your 

area of expertise.”349

Notwithstanding the valuable role that professional organizations can play in defining and 

enforcing ethical requirements, it must be noted that professional organizations can restrict 

 

345 Budowle, B., M. Bottrell, S. Bunch, et al. “A Perspective on Errors, Bias, and Interpretation in the Forensic 

Sciences and Direction for Continuing Advancement.” Journal of Forensic Sciences, 54 (July 2009): 803.

346 Scientific Working Group on Friction Ridge Analysis, Study and Technology. A Model Policy for Friction Ridge 

Examiner Professional Conduct. Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and 

Technology, December 2008.

347 ASCLD/LAB, op. cit., Principle 18.

348 Ibid., Principle 19. 349 European Network of Forensic Science Institutes Standing Committee for Quality and Competence. Performance 

Based Standards for Forensic Science Practitioners. European Network of Forensic Science Institutes Standing 

Committee for Quality and Competence, July 2004.
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ethically acceptable testimony as well as ethically dubious conduct. As noted in Chapters 1 and 

3, the International Association for Identification (IAI) passed a resolution in 1979 making it 

professional misconduct for any latent print examiner to provide courtroom testimony that 

labeled an identification “possible, probable, or likely,” rather than “certain.”350 Yet, the 

insistence on subjective certainty could produce a threshold that is too high—one that excludes 

testimony of an association that is less certain but still very useful to the trier of fact. Indeed, this 

norm has prompted the criticism that “fingerprint examiners are now unique among forensic 

analysts in that they are ethically bound to frame their conclusion in terms of absolute 

certainty.”351 

In 2010, IAI rescinded its 1979 resolution as “not consistent with advancements since [its] 

passage.”352 The new resolution states “that Resolution 1979-7 and Resolution 1980-5 are hereby 

rescinded” and approves of “a clear and unambiguous presentation” of “associations based on ... 

class characteristics (pattern type, ridge flow).” Whether the IAI will interpret this rescission as 

allowing its members to testify to degrees of confidence short of subjective certainty remains to 

be seen. Presumably, the “advancements” are “mathematically based models to assess the 

associative value of the evidence [that] may provide a scientifically sound basis for supporting 

the examiner’s opinion.”353 The resolution prevents an examiner from using a model that has not 

“been accepted as valid by the IAI” and warns that the “use of mathematically based models 

does not relieve the examiner of responsibility for their expert opinion.”354 Chapter 4 also 

discusses the importance of validating models and the need for the government to be open with 

data for validation studies. 

6.4 Expressions of Certainty

In Daubert v. Merrell Dow Pharmaceuticals, Inc.,355 the Supreme Court observed that “it would 

be unreasonable to conclude that the subject of scientific testimony must be ‘known’ to a 

certainty; arguably, there are no certainties in science.”356

 

350 International Association for Identification. “Resolution VII.” Identification News, 29 (August 1979). The next 

year the resolution was amended to make it clear that it applied only to examiners who made a probabilistic 

identification on their own initiative (rather than, say, under threat of a contempt citation). See International 

Association for Identification. “Resolution VII Amended.” Identification News, 3 (August 1980). Yet, analysts have 

departed from this constraint by testifying to possible matches. E.g., Warney v. Monroe County, 587 F.3d 113, 118 

(2d Cir. 2009).

 Thus, courts do not normally demand 

absolute certainty from scientists (or any other experts), but they do require more than 

conjecture. They exclude expert opinions that are so weak or speculative that they would not be 

helpful to a jury relative to the time they could consume and the misunderstandings they might 

generate. This is a special application of the broad principle that the trial judge should exclude 

even relevant evidence when “its probative value is substantially outweighed by the danger of 

351 Cole, S. “Fingerprinting: The First Junk Science?” Oklahoma City University Law Review, 28, no. 73 (2003): 88. 352 International Association for Identification. IAI Resolution 2010-18. International Association for Identification, 

July 16, 2010.

353 Ibid. 354 Ibid. 355 509 U.S. 579 (1993).

356 Ibid., p. 590.
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unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of undue 

delay, waste of time, or needless presentation of cumulative evidence.”357

In the medical discipline, to signal that an opinion was sufficiently definitive to be helpful, the 

practice of having physicians testify to diagnoses or other opinions in terms of “a reasonable 

degree of medical certainty” developed in many jurisdictions.358 In time, this practice spread to 

other professions and has led to scientists testifying “to a reasonable degree of scientific 

certainty.”359

Outside the courtroom, however, scientists do not communicate their findings in this fashion. An 

astronomer who reports the discovery of an exoplanet does not characterize the finding as 

satisfying some “reasonable degree of scientific certainty.” A chemist who deduces the identity 

of a compound from its nuclear magnetic resonance spectrum has no table of degrees of 

scientific certainty with which to label the deduction. Scientists might refer to personal degrees 

of confidence in a finding or to the degree of controversy surrounding it, but there is no generally 

accepted or working definition of a “reasonable degree of certainty” in scientific discourse.360 

The dissonance between the legal phrase and the scientific practice creates an issue for latent 

print examiners and forensic scientists of all types who are asked to use this phrase. When 

meeting with the attorney before trial, an expert not only should inform the attorney of the 

conclusion but also should specify the degree of confidence that can be expressed at trial. For 

example, an expert might explain to the attorney, and later in court, that although the discipline

does not normally use the phrase “reasonable degree of scientific certainty,” he is very confident 

in his conclusions based on his experience and the standards of the field. It is the lawyer’s 

responsibility to advocate for the admission of such testimony. Although individual trial judges 

could be skeptical of admitting testimony without the familiar accompanying words, it is clear 

that no rule of evidence requires the use of a phrase such as “reasonable degree of scientific 

certainty.”361 To the contrary, modern courts would not “expect dogmatic diagnoses from a 

careful scientist.”362

 

357 Federal Rules of Evidence 403.

358 For extreme examples of such testimony, see Cooey v. Strickland, 589 F.3d 210, 231 (6th Cir. 2009) (testimony 

“beyond a reasonable degree of medical certainty”); Lewicki v. Longshore, No. 17004/06, 2009 WL 4667411, at 2 

(N.Y. Sup. Ct. Dec. 7, 2009).

359 See Kaye, D. The Double Helix and the Law of Evidence. Harvard University Press, 2010. 360 In the social sciences and some other fields, it is conventional to regard a “p-value” of 0.05 as necessary to report 

a “statistically significant” finding. But this p-value is not a measure of the probability that the “null hypothesis” is 

true. Although the point is not always appreciated in the courtroom, the p-value refers to the probability of the data 

assuming that the hypothesis is true. See Kaye, D. and D. Freedman. “Reference Guide on Statistics.” In Reference 

Manual on Scientific Evidence edited by Committee on the Development of the Third Edition of the Reference 

Manual on Scientific Evidence and Committee on Science, Technology, and Law Policy and Global Affairs, 3d 

edition, pp. 211 – 302. National Academies Press, 2011. Consequently, it is not correct to say that one can have 95% 

confidence in the alternative hypothesis just because p < 0.05. That said, the similarities (or dissimilarities) in a pair 

of prints that would lead an examiner to declare an identification (or an exclusion) should be so extensive or clear as 

to produce a p-value that is considerably less than the conventional level of 0.05. 361 E.g., United States v. Willock, 696 F.Supp.2d 536, 574 (D.Md. 2010); United States v. Glynn, 578 F.Supp.2d 567, 

574 (S.D.N.Y. 2008). 

362 Amax Coal Co. v. Beasley, 957 F.2d 324, 328 (7th Cir.1992).
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Furthermore, even if a scientist is comfortable with the phrase, problems can arise. Some courts 

have rejected such testimony as an antidote to what they have deemed to be unjustifiably strong 

claims of identity. For example, some courts have concluded that the scientific foundation for 

absolute identification of toolmarks is insecure, but they still treat the matches discerned by 

skilled examiners as highly probative. This line of authority rejects statements of unique 

identification “as a matter of scientific certainty,”363 but permits it “within a reasonable degree of 

certainty in the firearms examination field,”364 “to a reasonable degree of ballistic certainty,”365

or only as being “more likely than not.”366 Similar reasoning has been applied to exclude 

assertions of scientific certainty for latent fingerprint identification testimony,367 although it 

remains to be seen whether such restrictions will displace the widely accepted practice of 

allowing expressions of absolute confidence in source attributions. 

6.5 Reliability, Validity, General Acceptance, and Prejudice

The courts that have constrained expressions of certainty about holistic pattern matching have 

done so to avoid outright exclusion of the evidence. Because scientific evidence might overly 

impress a jury, it is held to higher standards for admissibility than most other expert 

testimony.368 These are the “general acceptance” and scientific “reliability” standards.369 The 

general acceptance standard originated in the 1923 case of Frye v. United States.

370 In Frye, the 

U.S. Court of Appeals for the District of Columbia Circuit upheld the exclusion of testimony 

from a psychologist who used a blood-pressure cuff to determine that a defendant’s denial of a 

murder to which he had previously confessed was not the result of conscious deception. The 

Court of Appeals stated that 

just when a scientific principle or discovery crosses the line between the 

experimental and demonstrable stages is difficult to define. ... While courts will 

go a long way in admitting expert testimony deduced from a well-recognized 

scientific principle or discovery, the thing from which the deduction is made must 

be sufficiently established to have gained general acceptance in the particular 

field in which it belongs.371

 

363 United States v. Taylor, 663 F.Supp.2d 1170, 1180 (D.N.M. 2009). 364 Ibid. 365 United States v. Monteiro, 407 F.Supp.2d 351, 375 (D.Mass. 2006); Commonwealth v. Pytou Heang, 942 N.E.2d 

927 (Mass. 2011).

366 United States v. Glynn, 578 F.Supp.2d 567, 574-75 (S.D.N.Y. 2008). 367 United States v. Zajac, No. 2:06-cr-00811-CW (D. Utah Sept. 16, 2010).

368 Kaye, Bernstein, and Mnookin, op. cit., § 8.1.

369 Expert testimony generally is subject to a “reliability” inquiry in many jurisdictions because of the frequently 

partisan nature of expert testimony in the adversary system and the limited competence of judges and juries to 

evaluate expert reasoning. Kaye, Bernstein, and Mnookin, op. cit., Ch.1. “Reliability” here should not be confused 

with reliability in the statistical or scientific sense. Evidentiary reliability refers to a measurement process that is 

valid (it measures the quantity of interest), reliable (repeated measurements have low variance), and accurate (the 

measurements are close to the true values). Often, accuracy is considered an aspect of validity. E.g., Haber, L. and 

R. Haber. “Scientific Validation of Fingerprint Evidence Under Daubert.” Law, Probability & Risk, 7 (2008): 87. 

Whatever terms are used, such a process produces evidence that can be relied on. 370 293 F. 1013 (D.C. Cir. 1923).

371 Ibid. p. 1014.
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Over the years, Frye became the dominant test for scientific expert testimony in the United 

States.372 In the 1970s or so, however, an alternative standard that simply required scientific 

evidence to be especially reliable emerged in a significant minority of jurisdictions.373 

In 1993, the Supreme Court confirmed and accelerated this trend. In Daubert v. Merrell Dow 

Pharmaceuticals, Inc.,

374 plaintiffs alleged that a drug was a teratogen, but the Court of Appeals 

held that this theory lacked general acceptance because no published, peer-reviewed 

epidemiological studies demonstrated a statistically significant association between the drug and 

the type of birth defects experienced by the plaintiffs’ children. The Supreme Court held that, 

although the 1975 Federal Rules of Evidence were silent about whether they were perpetuating 

or abandoning Frye, they implicitly repudiated general acceptance as the sole requirement for 

scientific evidence. The Court wrote that while trial judges could continue to consider whether 

existing research has produced general scientific acceptance, this factor is not necessarily 

dispositive. Rather, the trial court should assess such additional factors as the extent to which the 

theory had been tested, the content of peer-reviewed publications, the existence of controlling 

standards in applying the technique, and the known error rate of the system.375 Only if this 

wide-ranging inquiry revealed that the theory and its implementation were “reliable” would the 

evidence satisfy Rule 702. Many state courts now apply the Daubert standard, but the Frye 

standard remains intact in other states. 

Finally, in 1999, the Supreme Court addressed a question left open in Daubert: whether 

nonscientific expert evidence was to be assessed with the factors articulated for the testimony of 

physicians, toxicologists, and epidemiologists at issue in Daubert itself. In Kumho Tire Co.

v. Carmichael,

376 the Court upheld the District Court’s exclusion of an engineer’s determination 

that a tire blew out because of a manufacturing defect as resting on an inadequately validated 

form of “visual and tactile inspection.” In doing so, it squarely rejected the Court of Appeals for 

the Eleventh Circuit’s view that “a Daubert analysis” applies only where an expert relies “on the 

application of scientific principles,” rather than “on skill- or experience-based observation.”377

The Kumho Court held that the trial court had the discretion to evaluate technical or experiential 

expert testimony in light of the factors listed in Daubert, but it added that “the test of reliability 

is ‘flexible,’ and Daubert’s list of specific factors neither necessarily nor exclusively applies to 

all experts or in every case.”378 The Court explained that 

Daubert’s general holding—setting forth the trial judge’s general ‘gatekeeping’ 

obligation—applies not only to testimony based on “scientific” knowledge, but 

also to testimony based on ‘technical’ and ‘other specialized’ knowledge. See 

Fed. Rule Evid. 702. We also conclude that a trial court may consider one or more 

of the more specific factors that Daubert mentioned when doing so will help 

determine that testimony’s reliability. But, as the Court stated in Daubert, the test 

 

372 Kaye, Bernstein, and Mnookin, op. cit., § 6.3.

373 Ibid., § 7.2.

374 509 U.S. 579 (1993). 375 Additional factors, such as whether the expert testing was done expressly for litigation, are enumerated in Kaye, 

Bernstein, and Mnookin, op. cit. 376 526 U.S. 137, 154 (1999). 377 Carmichael v. Samyang Tire, Inc., 131 F.3d 1433, 1435-36 (1997).

378 526 U.S. 141.
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of reliability is ‘flexible,’ and Daubert’s list of specific factors neither necessarily 

nor exclusively applies to all experts or in every case.379 

Daubert inspired many attacks on identification procedures that police laboratories routinely 

performed and that criminal courts universally accepted. If these procedures were held to the 

standards required for the approval of new drugs, or for a consensus among epidemiologists that 

a substance is a human carcinogen, it seemed that they might be tossed out of court. Latent 

fingerprint identification, long considered the gold standard for forensic identification 

techniques, was not immune from these challenges. In fact, in one noted case, a federal district 

judge—and a former dean of the law schools at the University of Pennsylvania and Yale 

University—ruled that because the ACE-V process failed to meet the Daubert test for scientific 

evidence, an examiner could not testify to an individualization (but could fulfill the teaching 

function of an expert by demonstrating to the jury the remarkable congruence in the images 

being compared); however, the court promptly reconsidered and vacated the order, reasoning that 

fingerprint testimony was as good as many other forms of skilled expert testimony.380 Judge 

Pollak wrote that 

I am not persuaded that courts should defer admission of testimony with respect 

to fingerprinting— ... ‘the bedrock forensic identifier of the 20th century’—until 

academic investigators ... have made substantial headway on a ‘verification and 

validation’ research agenda. Such research would be all to the good. But to 

postpone present in-court utilization of this ‘bedrock forensic identifier’ pending 

such research would be to make the best the enemy of the good.381

In other words, the judge emphasized the “flexibility” of Kumho over the earlier search for more 

extensive scientific validation. 

More recently, as noted in section 6.4, a small number of courts have curtailed the certainty with 

which a judgment of individualization of toolmarks may be expressed. They reason that enough 

scientific research and experience has been accumulated to establish the value of holistic pattern 

matching of toolmarks as a contribution of skilled witnesses, but these courts do not allow the 

prosecution or the expert witness to portray an individualization as the product of a rigorous, 

scientific technique.382

By insisting that holistic comparisons are rigorous scientific experiments, practitioners have 

invited challenges based upon the most demanding legal standards. Many latent print examiners 

are prone to emphasize that they follow the “scientific method.” A Federal Bureau of 

Investigation (FBI) publication, for example, maintains that “the ACE-V ... methodology, is a 

series of steps found within the scientific method,”383

 

379 Ibid. 

and SWGFAST defines ACE-V as “the 

380 United States v. Llera Plaza, Crim. No. 98-362-10, 11, 12, 2002 U.S. Dist. LEXIS 344 (E.D. Pa. Jan. 7, 2002),

vacated, 188 F. Supp. 2d 549 (E.D. Pa. 2002). 381 Ibid., p. 572.

382 E.g., United States v. Willock, 696 F.Supp.2d 536 (D.Md. 2010); United States v. Taylor, 663 F.Supp.2d 1170, 

1180 (D.N.M. 2009); Commonwealth v. Pytou Heang, 942 N.E.2d 927 (Mass. 2011). 383 Peterson, P., C. Dreyfus, M. Gische, et al. “Latent Prints: A Perspective on the State of the Science.” Forensic 

Science Communications, 11, no. 4 (October 2009). See also Cole, S. “Comment on Scientific Validation of 
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acronym for a scientific method.”384 Naturally, some witnesses express this view in their 

testimony. In State v. Foreman,

385 a latent print examiner from Connecticut’s state forensic 

laboratory with “extensive qualifications” testified that “our comparisons are conducted through 

a scientific methodology known as ACE-V.”386 During cross-examination, he reiterated that 

“based on our training, education, experience, based on fact and history of fingerprints, 

fingerprints is a science. As I explained earlier, the comparison methodology using ACE-V 

methodology is a scientific methodology.”387 

As we have seen, however, when confronted with serious controversy over the scientific nature 

of inferences from a technique or procedure that is portrayed or perceived as highly scientific, 

the proponent of the evidence must demonstrate sufficient scientific studies to establish the 

technique’s validity or its general acceptance (depending on the jurisdiction). When the process 

is more intuitively accessible and is not heavily wrapped in the rhetoric of science, courts 

dispense with a showing of scientific validation or general scientific acceptance.388 In particular, 

courts impressed with the Daubert objections to toolmark and fingerprint identification have 

emphasized the flexibility provided by Kumho to admit the evidence, at least where the expert 

does not attest to scientific certainty.389 Testimony that the evaluation process is strictly scientific 

or produces scientifically certain results thus undermines the theory that some courts have used 

to overcome Rule 702 objections. 

Proponents of expert testimony may need to be aware of two other issues. First, evidence must 

be such that its probative value is not substantially outweighed by its prejudicial effect.390 The 

proponent must also assess whether a debate over how to label the expert’s approach—as a 

“scientific” method—could divert the jury’s attention from the adequacy of the examiner’s 

conclusions in the particular case. As noted in Chapters 1 and 3, ACE-V maps the steps of a 

process, but it does not provide specific functional guidance on how to carry out that process nor 

does it detail what the substantive content of those various steps should be. As a result, the legal 

and scientific literature contains assertions that “merely following the steps of ACE-V does not 

imply that one is proceeding in a scientific manner,”391

 Fingerprint Evidence Under Daubert.” Law, Probability & Risk, 7, no. 119 (2008): 123 (collecting similar 

statements).

that the invocation of the scientific 

384 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Glossary, Version 2.0. Scientific 

Working Group on Friction Ridge Analysis, Study and Technology, May 2009.

385 State v. Foreman, 954 A.2d 135 (Conn. 2008). 386 Ibid., p. 155, note 19. 387 Ibid. 388 E.g., Ex parte Dolvin, 391 So.2d 677, 679 (Ala. 1980); People v. Clark, 857 P.2d 1099 (Cal. 1993); State v. Reid,

757 A.2d 482, 487 (Conn. 2000); Carter v. State, 766 N.E.2d 377 (Ind. 2002). See generally Kaye, Bernstein, and 

Mnookin, op cit.; McCormick, op. cit. 389 See, e.g., United States v. Baines, 573 F.3d 979, 992 (10th Cir. 2009); United States v. Llera Plaza, Crim. No. 

98-362-10, 11, 12, 2002 U.S. Dist. LEXIS 344 (E.D. Pa. Jan. 7, 2002), vacated, 188 F. Supp. 2d 549 (E.D. Pa. 

2002). Compare United States v. Gutierrez-Castro, 86 Fed. R. Evid. Serv. 319 (D.N.M. 2011) (allowing an 

examiner “to testify about the methods and practices of inked fingerprint analysis, and to ... testify that all the 

fingerprints belong to the same person,” but ordering that “[t]he United States may not, ... offer [him] as an expert 

witness in the jury’s presence, the Court will not certify [him] as an expert witness in the jury’s presence, and the 

jury instructions will not refer to [him] as an expert witness”).

390 See Federal Rules of Evidence 403; McCormick, op. cit. 391 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 142.
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method is only an “analogy,”392 that “ACE-V is an acronym, not a methodology,”393 that it is “a 

broadly stated framework”394 better described as “common sense,”395 and that “the ACE-V 

protocol remains obscure”396 because it rests on “an ill-defined, flexible, and explicitly 

subjective criterion.”397 Such statements are listed not to endorse them and not to decide the 

semantic or philosophical question of whether ACE-V is scientific.

398 Instead, these statements 

suggest that objections based on the premise that it is prejudicial to describe ACE-V as “science” 

can be avoided by referring to ACE-V as a systematic and widely used process for determining 

whether two patterns have a common origin. 

Second, advances in computer pattern matching for fingerprint identification can be expected to 

come before the courts, and these surely will have to be evaluated under the Frye or Daubert 

standard for pure scientific evidence. For example, as explained in Chapter 4, automated systems 

can measure the distance (in an abstract mathematical space) between certain features in two 

images. They can generate probabilities for such distances under the assumption that the image 

of the unknown print comes from a finger known to have produced an exemplar and that it came 

from a finger of a randomly selected individual represented in a reference set of exemplars from 

many individuals. Such conditional probabilities (also known as “likelihoods”), if they rest on 

adequate data and valid models, might be used in their own right or to reinforce (or contradict) 

the judgments of a human examiner. Before this can happen in a jurisdiction that applies the 

general acceptance standard, scientific studies validating the automated system must convince 

the scientific community that it is reliable and accurate for this particular use. In jurisdictions that 

follow Daubert, a court should assess factors such as the extent of peer-reviewed publications 

and the known error rate of the system to assure itself that the theory and its implementation are 

scientifically sound. 

6.6 Errors and Error Rates

Chapter 2 describes the major types of errors in examining two impressions to determine whether 

they came from the same source. It notes cases in which expert witnesses assured courts that the 

ACE-V process, if followed faithfully, could not err, and it covers the resulting criticisms from 

commentators, courts, and even within the latent print community. Assertions that false 

identifications occur at a rate of less than one in a million comparisons have not fared well either. 

Precise estimates of error rates, based on empirical research with a large number of cases in 

which ground truth was established, were not available. Yet, virtually all courts accepted expert 

testimony that fingerprint identifications and exclusions were absolutely certain to be correct.

In several other fields, where controlled experiments or field studies have been conducted, many 

court opinions treat the observed error rates of scientific tests as a consideration affecting the 

admissibility of these tests or the weight to be given to the results in a particular case. For 

 

392 Haber and Haber, op. cit., p. 98. 393 Zabell, S. “Fingerprint Evidence.” Journal of Law and Policy, 13 (2005): 143. 394 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 142. 395 Zabell, op. cit., p. 178.

396 C. Champod, op. cit., p. 114. 397 Stoney, D. “Measurement of Fingerprint Individuality.” In Advances in Fingerprint Technology, edited by Henry 

C. Lee and R.E. Gaensslen, 327–87. 2nd ed. CRC Press, 2001.

398 On this issue, see Cole, 2008, op. cit. 
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example, a significant body of controlled experiments and field studies of the accuracy of 

polygraphic lie detection has informed opinions on the admissibility of this type of evidence.399

A smaller set of laboratory experiments of visual spectrographic speaker identification also is 

available.400 

Until very recently, almost no experimental studies of the accuracy of the latent print 

examination process existed.401 In 2011, the results of a major experiment, known as the NoblisFBI experiment, were published.402 Because of the size and careful design and execution of the 

study, it is sure to play a role in litigation on the admissibility of latent print evidence. As 

explained in Chapter 2 (Box 2.4), 169 latent print examiners each were presented with 100 pairs 

of latent and exemplar prints. In the more than 10,000 presentations deemed of value for 

individualization, 97% of the examiners made no false identifications; the remaining 5 examiners 

made a total of 6 false identifications, for a false positive rate of about 0.1%. The examiners 

made 450 false exclusions for prints deemed of value for identification or exclusion, for a false 

negative rate of about 7.5%.403 However, the examiners who volunteered for the experiment 

were not a random sample of all examiners, and although the latent prints were chosen to be 

representative of casework, the pairings as a group could have been more (or less) challenging 

than typical casework. Thus, there is room for additional research on errors and for caution in 

applying the measurements of error rates in this study to the performance of particular examiners 

in specific cases.

Some observers have proposed using existing proficiency test results (or more rigorous, blind 

tests) to produce estimates of or bounds on error rates for a particular examiner, for a given 

laboratory, or for the field as a whole.404 As noted in Chapter 3, whether this procedure can 

produce reasonably precise estimates of the probability of a false positive or negative in a 

particular case is questionable. The issue is hardly new.405

 

399 For a review, see National Academy of Sciences, National Research Council, Committee to Review the Scientific 

Evidence on the Polygraph, The Polygraph and Lie Detection, 2003.

 Although the 2009 NRC report is 

silent about the value of proficiency test results as an indication of case-specific error rates, two 

400 For reviews, see Bolt, R., F. Cooper, E. David, et al. “Speaker Identification by Speech Spectrographs: Some 

Further Observations.” Journal of the Acoustical Society of America, 54 (1973): 531; Kent, R. and M. Chial. “Talker 

Identification: Scientific Status.” In Modern Scientific Evidence: The Law and Science of Expert Testimony edited 

by Faigman, D., M. Saks, J. Sanders, et al., vol. 1, pp. 113 – 151. Thomson Reuters/West, 2009.

401 Limited data come from the United Kingdom (Evett, I. and R. Williams. “A Review of the Sixteen Points 

Fingerprint Standard in England and Wales.” Journal of Forensic Identification, 46, no. 1 (1996): 49), from 

proficiency tests in Australia (Gutowski, S. “Error Rates in Fingerprint Examination: The View in 2006.” The 

Forensic Bulletin, Autumn 2006, 18), and from a study of six examiners in Minnesota (Langenburg, G. “A 

Performance Study of the ACE-V Process: A Pilot Study to Measure the Accuracy, Precision, Reproducibility, 

Repeatability, and Biasability of Conclusions Resulting from the ACE-V Process.” Journal of Forensic 

Identification, 59, no. 2 (2009): 219 – 57). 402 Ulery, B., A. Hicklin, J. Buscaglia, et al. “Accuracy and Reliability of Forensic Latent Fingerprint Decisions.” 

Proceedings of the NAS. 2011.

403 Not counting outcomes of “inconclusive,” the figures are 0.2% and 10.2%, respectively. See Chapter 2 (Table 

2.9).

404 E.g., Koehler, J. “Fingerprint Error Rates and Proficiency Tests: What They Are and Why They Matter.” 

Hastings Law Journal, 59 (2008): 1077; Teichroeb, R. “Produce Crime Lab Error Rates, Some Urge.” Seattle

Post-Intelligencer, July 21, 2004. Accessed November 28, 2011. http://www.seattlepi.com/default/article/Producecrime-lab-error-rates-some-urge-1149873.php. 405 E.g., Berger, M. “Laboratory Error Seen Through the Lens of Science and Policy.” University of California 

Davis Law Review, 30 (1997): 1081.
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previous NRC reports on DNA evidence discuss the topic. A 1992 committee favored the 

production of proficiency test results as trial evidence.406 A 1996 committee did not go this far, 

but it supported the disclosure of test results in reports.407 Building on these ideas, defendants 

have argued that evidence of a DNA match should be inadmissible unless this information 

accompanied it. The courts consistently rejected the argument.408 

A defendant might seek to introduce statistics to show that examiners as a group do not have 

perfect scores on proficiency tests or that the specific witness has made false positive or negative 

findings in the past.409 In response to this defensive use of error rates, it has been argued that the 

use of an average statistic is “not meaningful” because not all examiners are equal and that 

“cumulative error over time is not a meaningful mechanism for assessing current error rate” in 

that steps inevitably will be taken to correct errors.410 

Both statements are problematic. First, the mean is generally a reasonable estimator of the scores 

of the members of a group. If other information on individuals is available, adjustments can be 

made to the mean for those individuals.411 If no other information is available, using the sample 

mean is still more accurate than random guessing. Second, even if a process is improving over 

time, using a recent average is likely to be more accurate than random guessing. Therefore, the 

statistics cannot be dismissed as meaningless, but their utility remains debatable. As one group of 

latent print examiners argue, 

calculating human error rates is a complex undertaking, because unlike 

instruments, human beings change, learn, and adapt, particularly when faced with 

errors and the quality assurance systems designed to overcome these errors and 

improve practices. As a result, the chance that human errors will be made or 

repeated is constantly changing.412

No published appellate opinions seem to have considered the admissibility of error-rate statistics 

under the principles of Federal Rules of Evidence 403 and 404.413 In Williams v. State,

414

Maryland’s highest court reversed a conviction because “the trial judge erred in restricting 

Williams from fully cross examining [the DNA analyst] concerning the prevalence of testing 

errors and contamination during PCR [polymerase chain reaction] testing at Cellmark.”415

 

406 National Academy of Sciences, National Research Council, Committee on DNA Technology in Forensic 

Science. DNA Technology in Forensic Science. National Academies Press, 1992.

The 

407 See Kaye, The Double Helix and the Law of Evidence, 2010, op. cit., pp. 162–170.

408 Ibid. 409 Six out of the one hundred sixty-three examiners who responded to questions about “ever having made an 

erroneous individualization (after training)” in the Noblis-FBI study reported that were aware of at least one such 

error. (All but one of these occurred during proficiency tests or were detected during verification.) Fifty-six out of 

one hundred sixty-seven responding examiners reported awareness of “an erroneous exclusion (after training),” and 

ten of these were “on casework: detected after it was reported to contributor.” Ulery, Hicklin, Buscaglia, et al., op. 

cit.

410 Budowle, Bottrell, Bunch, et al., op. cit. 411 Koehler, op. cit. 412 Peterson, Dreyfus, Gische, et al., op. cit. 413 For an argument against admissibility, see Imwinkelried, E. and D. Kaye. “DNA Typing: Emerging or Neglected 

Issues.” Washington Law Review, 76 (2001): 413. 414 Williams v. State, 679 A.2d 1106 (Md. 1996).

415 Ibid., p. 1120.
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court specifically rejected “the State’s contention that ‘It does not matter if fifty percent of their 

cases were contaminated. What matters is this one.’”416 Of course, whatever the result as to the 

admissibility of errors in other cases, the trial judge has discretion to exclude past errors that are 

not very probative. Indeed, exclusion would seem to be required if the past errors could not have 

recurred as a result of corrective action. 

Given the emphasis on error rates in post-Daubert opinions, an expert who testifies to an 

individualization should understand that a false positive error could arise, in theory, for at least 

two logically distinct reasons.417 One is the possibility that somewhere in the world, another 

individual has a finger that could have produced a latent print with the same distinctive features 

noted in the latent print in the case. The other is that the examiner erred in identifying the 

distinctive features or gauging their distinctiveness. A witness can concede that these are logical 

possibilities—that there are no absolute certainties—without altering an opinion that the 

defendant is very likely to be the source of a high-quality latent print. Indeed, in presenting the 

opinion, it might be wise to describe the steps taken to avoid observational and judgmental error. 

Consequently, the Working Group recommends: 

Recommendation 6.3: A testifying expert should be familiar with the literature related 

to error rates. A testifying expert should be prepared to describe the steps taken in the 

examination process to reduce the risk of observational and judgmental error. The 

expert should not state that errors are inherently impossible or that a method 

inherently has a zero error rate. 

Recommendation 6.3 is not limited to individualization testimony. A witness who testifies to the 

strength of the evidence without stating that the defendant is the only possible source of the 

unknown print, as described below in section 6.7, can explain that the evidence is extremely 

strong, in part because of the protections against erroneous ascertainment of the relevant 

features, the verification by other examiners,418 and the fact that the images are available for 

verification by still more experts. However, care must be taken in testifying or arguing that a 

defendant failed to do an independent re-analysis. Suggesting that the defendant has an 

obligation to verify the findings would be constitutionally objectionable. Nonetheless, if the 

defendant raises the issue, the prosecution should be permitted to disclose the fact that other 

experts can confirm (or refute) a reported match.419 

 

416 Ibid. See also State v. Proctor, 595 S.E.2d 480 (S. Car. 2004) (regarding proficiency test results as potential 

impeachment evidence that must be disclosed to the defense under Brady v. Maryland). 417 See Kaye, Bernstein, and Mnookin, op. cit. 418 Such testimony is routinely received as part of the explanation of the “V” in ACE-V, but its admissibility could 

be challenged under the hearsay rule and the Confrontation Clause. On the hearsay problem, see Bunche v. State, 

5 So.3d 38, 40 n.1 (Fla. Dist. Ct. App. 2009) (collecting conflicting cases). 419 Imwinkelried and Kaye, op. cit.; National Academy of Sciences, National Research Council, Committee on DNA 

Forensic Science: An Update. The Evaluation of Forensic DNA Evidence. National Academies Press, 1996, pp. 

182–183.
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6.7 Terminology

The 2009 NRC report observes that 

many terms are used by forensic examiners in reports and in court testimony to 

describe findings, conclusions, and the degrees of association between evidentiary 

material (e.g., hairs, fingerprints, fibers) and particular people or objects. Such 

terms include but are not limited to “match,” “consistent with,” “identical,” 

“similar in all respects tested,” and “cannot be excluded as the source of.”420

According to the committee, the fact that “the forensic science disciplines have not reached 

agreement or consensus on the precise meaning of any of these terms” is a “critical” problem.

However, clarity would seem more important than uniformity. From the jurors’ standpoint, it is 

not obvious why every testifying expert in every field must use the same phrase to describe a 

given degree of association. When the expert defines words such as “match” or “identical” in the 

course of the testimony, the choice of one particular synonym over another should not confuse 

jurors. What is critical is that the degree of similarity be accurately ascertained and conveyed and 

that the implications of the observed degree of similarity be described fairly and clearly. 

Unfortunately, disagreement exists regarding what terminology is most appropriate and 

warranted. Therefore, this section describes the traditional forms of testimony about an 

examiner’s findings, along with several possible alternatives that are at least as well founded in 

our current knowledge of the nature of latent prints and the cognitive capacities of human 

examiners. The purpose of explicating such alternative formulations is not to insist on the use of 

any single set of terms but to canvass the range of potentially admissible testimony about the 

implications of the observed similarities and differences between an unknown print and an 

exemplar. 

6.7.1 Reporting an Exclusion, Match, or Inconclusive Result 

All of the disciplines that strive to associate a trace with its source involve two logical steps: 

(1) measuring the similarities and differences between two samples, and (2) assessing the 

significance of the measurements.421 The measurements pertain to properties of the material or 

mark (e.g., the refractive index of glass, the color of hair, the sizes of DNA fragments, or the 

concentrations of elements). The significance of finding corresponding characteristics in a pair of 

samples depends on how often the combination of those characteristics arises when the samples 

come from the same source as opposed to when they originate from different sources. 

A quantity that captures this idea is the likelihood ratio. As previously explained (Chapters 1 and 

4), the likelihood ratio states how many times more probable the measurements are when the

hypothesis of a common source (s) is true than they are when the hypothesis of a disparate 

sources (d) is true. When the likelihood ratio is exactly one—when the measured similarities in a 

 

420 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 185. 421 Kaye, D. “Interpretation: A Legal Perspective.” In Wiley Encyclopedia of Forensic Sciences edited by A. 

Moenssens and A. Jamieson, vol. 3, pp. 1561–65. J. Wiley & Sons, 2009.
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pair of items is as probable for a common source as a disparate one—the analysis is of no value 

in informing a decision between these two possibilities. The evidence is logically and legally 

irrelevant.422 On the other hand, when the measurements are far more probable for a common 

source than for different sources, they are strongly probative of identity (s). 

Testimony from examiners who perform pattern matching for identification normally reflects 

these two steps of measurement and inference. All the phrases quoted in the NRC report—

“match,” “consistent with,” “identical,” “similar in all respects tested,” and “cannot be excluded 

as the source of”—merely express a finding that the measured features in the two samples being 

compared show a degree of correspondence. Conversely, when the measurements do not 

correspond, an examiner may testify to an “exclusion.” An exclusion means that the 

measurements on the two items are so different that they would never (or almost never) arise 

when the items have a common source, while the measurements could easily be this different 

when the items come from different sources. Thus, when two fingerprints are so different that 

they almost certainly could not have come from the same finger, an examiner, via the ultimately 

subjective process of “evaluation” described in Chapter 3, may conclude that the finger that 

produced the known print did not produce the questioned print. Finally, a forensic analyst may 

decline to reach a conclusion about the origin of a trace, such as when an examiner decides that a 

latent print is not even worth comparing (“not suitable”) or that a pair of impressions is worth 

studying further but that they have too few clear similarities or dissimilarities to warrant a 

reasonable judgment of inclusion or exclusion (“inconclusive”). 

6.7.2 Describing the Significance of a Match: Global Individualization 

The second aspect of pattern matching—describing the significance of the observed degree of 

matching—has proven contentious in all fields of forensic identification.423 For this reason, it is 

important to consider a spectrum of possible modes of presentation, ranging from the very 

powerful assertion that every finger leaves marks that are distinguishable from those of every 

other finger (when the marks are of sufficient quality and extent) to the very weak claim that an 

observed degree of similarity is at least slightly more likely if the items being compared 

originated from the same source than if they came from different sources. 

The traditional form of testimony in the field of latent print identification is source attribution 

based on the theory of universal individualization (Chapter 1). One survey of the field explains 

that

in the friction ridge discipline, an individualization is often reported as, “One 

latent fingerprint detected on a demand note has been identified as a fingerprint of 

JOHN DOE.” Similarly, when testifying, an examiner often describes the 

individualization conclusion with a statement such as, “The latent print on 

Government’s Exhibit 10, a revolver, and the fingerprint recorded in the right 

index finger block on the fingerprint card bearing the name ‘John Doe’ originated 

from the same source.”424

 

422 McCormick, op. cit., § 185.

423 Giannelli and Imwinkelried, op. cit.; Faigman, Kaye, Saks, et al., op. cit.; Kaye, Bernstein, and Mnookin, op. cit. 424 Peterson, Dreyfus, Gische, et al., op. cit. See also Cole, S. “Where the Rubber Meets the Road: Thinking About 

Expert Evidence as Expert Testimony.” Villanova Law Review, 52 (2007): 803.
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Some witnesses combine statements of individualization with expressions of absolute certainty, 

as in United States v. Hugh,

425 where “the government’s fingerprint expert ... testified that he 

was ‘100 percent, without a doubt’ certain that ‘the latent print is that of Nolan Hugh.’” 

Such testimony has the virtue of stating clearly and unequivocally the examiner’s opinion of 

what the observed degree of similarity establishes: that the suspect’s finger is the source of the 

latent print. Opinions of “universal individualization” like this one rest on a theory of “universal 

general uniqueness.”426 In a Massachusetts case, for example, the expert “stated that the prints 

had been ‘individualized’ to a Samantha Rivera, and defined the word ‘individualized’ as 

meaning ‘to the exclusion of all others.’”427 This is the classical understanding of 

“individualization” in forensic science, although, as noted in Chapters 1 and 3, there has been 

some movement toward using the term to mean any definitive identification of a single 

individual as the source of a latent print. 

Until published studies address the criticisms of universal individualization outlined in Chapter 

1, challenges under Rule 702 to the admissibility of absolute statements of individualization will 

continue. Except for a handful of unreported decisions,428 challenges to the admissibility of 

individualization under the existing ACE-V process have failed,429 but the NRC report lends new 

fuel to attacks on universal individualization testimony. In addition to characterizing ACE-V as 

un-validated and of doubtful reliability,430 the report endorses the view that “in order to pass 

scrutiny under Daubert, fingerprint experts should exhibit a greater degree of epistemological 

humility. Claims of ‘absolute’ and ‘positive’ identification should be replaced by more modest 

claims about the meaning and significance of a ‘match.’”431 To consider how this could be 

accomplished, the next several sections consider some alternatives to the traditional 

individualization testimony that was based on the theory of global general uniqueness. 

6.7.3 Describing the Significance of a Match: Specific Individualization

In a particular case, same-source testimony might be justified even if the claim of universal 

general uniqueness were rejected. Imagine a particular case in which only two individuals could 

have left the latent print, and an exemplar for one of these two individuals (but not the other) is 

 

425 United States v. Hugh, No. Crim.A. 03-829, 2009 WL 212420 (E.D. Pa. Jan. 28 2009). 426 Kaye, D. “Identification, Individualization and Uniqueness: What’s the Difference?” Law, Probability & Risk, 8 

(2009): 85.

427 Commonwealth v. Gambora, 933 N.E.2d 50, 56 (Mass. 2010). 428 See Page, M., J. Taylor, and M. Blenkin. “Forensic Identification Science Evidence Since Daubert: Part II—

Judicial Reasoning in Decisions to Exclude Forensic Identification Evidence on Grounds of Reliability.” Journal of 

Forensic Sciences, 56 (2011): 913 – 917. The best known opinions come from a state trial judge in Maryland and 

from federal trial judges in Pennsylvania and Utah. State v. Rose, No. K06-0545 (Md. Cir. Ct. Oct. 19, 2007); 

United States v. Llera Plaza, Crim. No. 98-362-10, 11, 12, 2002 U.S. Dist. LEXIS 344 (E.D. Pa. Jan. 7, 2002),

vacated, 188 F. Supp. 2d 549 (E.D. Pa. 2002); United States v. Zajac, No. 2:06-cr-00811 CW (D. Utah Sept. 16, 

2010). 

429 No reported appellate court opinion has limited testimony of individualization. See U.S. Department of Justice, 

Office of the Inspector General. A Review of the FBI’s Progress in Responding to the Recommendations in the 

Office of the Inspector General Report on the Fingerprint Misidentification in the Brandon Mayfield Case. U.S. 

Department of Justice, 2011, p. 20, note 22 (listing federal circuit court opinions). 430 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 142.

431 Ibid. (quoting Mnookin).
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available. Furthermore, there is an excellent match between the latent and the exemplar, and the 

probability of this degree of matching in a finger from a randomly selected individual is a mere 

one in one trillion. Then the chance that the other (untested) individual also matches is one in one 

trillion. Now, if the potential suspect population were even slightly larger, say, three individuals, 

then the chance of a match to either the second or the third untested individual also would be 

larger—about two in one trillion. If the suspect population were larger still—say, one thousand 

people—then the chance of a match to at least one of these one thousand people would be 

roughly one thousand out of one trillion (i.e., one in one billion). In all these small populations,

the chance of a duplicate fingerprint is so small that one can be confident that no other match 

would be found. 

The FBI uses such reasoning to make source attributions for DNA evidence when the estimated 

random-match probability for the specific DNA profile is very small relative to the suspect 

population.432 Courts have upheld these source attributions despite defense arguments that 

untested relatives might match or that the laboratory could have erred.433 The assertion is not that 

every identifying DNA profile is unique in all populations, but only that the probability of 

finding no other matching profiles in a smaller population (such as that of the United States) is 

close to one. For a one-in-one-trillion probability of a random match to a particular DNA profile, 

for example, the probability that no unrelated resident of the United States would match that

profile is approximately 1 – (3 × 108

) × 10–12 = 0.997. 

This reasoning differs from the theory of global individualization of fingerprints in two respects. 

First, the DNA computation pertains only to the population of the United States and not to the 

much larger population of the entire world. Second, the DNA computation does not purport to 

show that every DNA profile in the smaller population is unique to an individual (and any 

identical twin of that individual). Rather, the computation merely gives the probability that the 

one profile that has been observed to match the suspect is duplicated in a population of unrelated 

individuals. The latter difference is often analogized to the famous Birthday Paradox. You can be 

pretty sure that if you are in a room with 22 other people, your birthday is unique to you. If every 

birthday is equally frequent in the population and if leap years are ignored, the probability is [1 – 

(1/365)]23 = 0.94. But it is more probable than not (p = 0.5073) that at least one pair of people in 

the room has the same birthday. A specific birthday probably is unique in the room, but 

birthdates are probably not a unique identifier, even in this small population.434 

For single-source testimony to be admissible under the theory that the random-match probability 

is so small that the duplication probability in a particular region is negligible, the expert would 

need to have a reasonable estimate of the random-match probability, or at least an upper bound 

on this quantity. Statistical models of fingerprint features date back to Galton, but the early 

models suffer from reliance on untested assumptions of independence and the failure to take into 

 

432 Budowle, B., R. Chakraborty, G. Carmody, et al. “Source Attribution of a Forensic DNA Profile.” Forensic 

Science Communications, 2, no. 3 (2000); Kaye, D. and G. Sensabaugh. “Reference Guide on DNA Evidence.” 

Reference Manual on Scientific Evidence. 3rd ed. National Academies Press, 2000.

433 United States v. Davis, 602 F.Supp.2d 658 (D.Md. 2009); People v. Cua, 119 Cal.Rptr.3d 391 (Cal. Ct. App. 

2011); Young v. State, 879 A.2d 44 (Md. 2005). 434 For discussion in the context of DNA evidence, see NAS, NRC, Committee on DNA Forensic Science: An 

Update, op. cit.
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account the spatial relationships of features, distortion, and variability among examiners.435

Recent work is intended to address these limitations, and it is possible that a basis for opinions of 

the individuality for some latent prints in various populations can be established.436 

6.7.4 Describing the Significance of a Match: Random-Match Probabilities

Although specific-individualization testimony has been held admissible for DNA typing, the 

usual testimony is that there is a high degree of similarity and a low probability of such similarity 

when the defendant is not the source (but coincidentally possesses similar physical features). 

When good estimates of the frequency of the feature set exist, a numerical probability statement 

is admissible in court.437

The statistical models for DNA frequencies, being based upon theories of population genetics 

and data from many samples, are not of much help with more complex patterns such as 

fingerprints that result from different random processes. However, data-driven statistical 

analyses of feature combinations could provide highly conservative estimates that should be 

admissible. When such “improbability testimony” was presented in the past, however, it rested 

on an inadequate scientific foundation. For example, in Commonwealth v. Drayton,

438 

a fingerprint expert, duly qualified, testified that fingerprints found on the wooden 

box and prints taken from the defendant showed twelve “points of similarity,” and 

stated his opinion that the fingerprints on the box were those of the defendant. On 

redirect examination, the prosecutor asked the witness to give his opinion on the 

statistical probability that prints with twelve points of similarity could be made by 

two different people. The witness replied that “there is a figure of one out of 387 

trillion.”439

On appeal from the resulting conviction, the Supreme Judicial Court of Massachusetts held that 

although the probability should have been excluded because it “lacked foundation and exceeded 

the witness’s expertise,”440 the “brief, cumulative statement concerning statistics was 

harmless.”441 

Modern databases and computer technology are capable of providing more defensible probability 

estimates. One prominent researcher noted that 

 

435 See Pankanti, S., S. Prabhakar, and A. Jain. “On the Individuality of Fingerprints.” IEEE Transactions on Pattern 

Analysis and Machine Intelligence, 24, no. 8 (2002): 1010; Stoney, 2001, op. cit. Claims of global uniqueness 

founded on older estimates of random-match probabilities are therefore suspect. Yet, such claims persist in 

textbooks. E.g., Houck, M. and J. Siegel. Fundamentals of Forensic Science. 2nd ed. Academic Press, 2010, pp. 484 

– 485.

436 See Chapter 4; Kaye, D. “Probability, Individualization, and Uniqueness in Forensic Science Evidence: Listening 

to the Academies.” Brooklyn Law Review, 75 (Summer 2010): 1163. 437 The development of this legal doctrine is traced in Kaye, The Double Helix and the Law of Evidence, 2010, op. 

cit.

438 Commonwealth v. Drayton, 434 N.E.2d 997 (Mass. 1982).

439 Ibid., p. 1005. 440 Ibid. 441 Ibid., p. 1006. Another case that involved a dubious probability calculation is Hicks v. Schurr, 871 F.2d 255 (8th 

Cir. 1982). 
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systematic research on the selectivity of fingerprint features [points] towards an 

extreme selectivity of these features, even when partial and limited information is 

considered. ... For example ... even very limited configurations of fingerprint 

minutiae can provide very powerful evidence with match probabilities in the order 

of 1 in a billion, even without considering the statistical contribution of level 1 

features (general pattern, ridge counts, etc.) or other fingerprint features if 

available.442

In the words of one forensic science textbook, “no standard model for random-match 

probabilities has been adopted for forensic fingerprint casework, but that day is coming.”443

6.7.5 Describing the Significance of a Match: Strength of Evidence

In the types of testimony considered so far, the expert expresses a categorical opinion about who 

is the source of a latent print or the probability of a match if an individual other than the 

matching suspect is the source. A substantial body of literature urges forensic scientists to 

eschew both of these approaches and to confine their testimony to statements about how 

probable the evidence is when the defendant, as opposed to another (perhaps randomly selected) 

individual, is the source—that is, to presenting likelihoods or likelihood ratios.444 

In this likelihood approach, the forensic scientist or analyst never gives an opinion about the 

prosecution’s claim that the defendant is the source. Rather, the expert describes in words or 

numbers the chances of seeing the evidence in two situations: (1) when the defendant is the 

source and (2) when someone else is. As noted earlier, the ratio of these quantities, the likelihood 

ratio, measures the strength of the evidence in favor of identity. The NRC report implicitly 

endorses this mode of reporting when it states that 

although some disciplines have developed vocabulary and scales to be used in 

reporting results, they have not become standard practice. This imprecision in 

vocabulary stems in part from the paucity of research in forensic science and the 

corresponding limitations in interpreting the results of forensic analyses. 

Publications such as Evett et al., Aitken and Taroni, and Evett provide the 

essential building blocks for the proper assessment and communication of 

forensic findings.445

Evett and other forensic scientists propose the following table for “reporting the value of the 

support of the evidence.” 

 

442 Champod, op. cit., p. 113. 443 Houck and Siegel, op. cit., p. 485. 444 E.g., Aitken, C. and F. Taroni. Statistics and the Evaluation of Evidence for Forensic Scientists. 2nd ed. John 

Wiley & Sons, 2004, pp. 414 - 419; Buckleton, J., C. Triggs, and C. Champod. “An Extended Likelihood Ratio 

Framework for Interpreting Evidence.” Science & Justice, 46 (2006): 69; Robertson, B. and G. Vignaux. 

Interpreting Evidence: Evaluating Forensic Science in the Courtroom. John Wiley & Sons, 1995.

445 NAS, NRC, Committee on Identifying the Needs of the Forensic Science Community, op. cit., p. 186.
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Range of Likelihood Ratio Strength of Evidence

1 < LR ≤ 10 Limited evidence to support

10 < LR ≤ 100 Moderate evidence to support

100 < LR ≤ 1000 Moderately strong evidence to support

1000 < LR ≤ 10000 Strong evidence to support

10000 < LR Very strong evidence to support

Table 6.1: Strength of likelihood ratios in support of evidence446

Decades ago, a similar mapping, ranging from “not useful” (LR < 4) to “practically proved” (LR 

≥ 499), became the norm in the parentage testing community.447 

Modern proponents of likelihood-based presentations argue that “the fingerprint profession has 

to recognize that conclusions of identification to the exclusion of all others are essentially outside 

the realm of the expert witness. ... Testimony should limit itself to expressing the contribution of 

the findings in favor of one proposition (identity of sources) versus another (nonidentity of 

sources).”448 In Europe, the Association of Forensic Science Providers has described how 

practitioners can implement this approach to expert evaluations of evidence.449 Even when 

precise values of the likelihood ratio for a type of evidence is not available, an expert can rely on 

subjective probabilities in a table, such as the one above, to describe the weight of the evidence 

without taking the further step of drawing a conclusion about what the evidence proves. In a 

fingerprint case, an examiner using this framework might testify that the degree of similarity (a 

“match”) is “very strong” evidence that the latent print originated from the defendant’s finger450

because, based on what is known in the field, it is far more probable that this degree of similarity 

would occur when comparing the latent print with the defendant’s fingers than with someone 

else’s fingers. This is certainly a more modest claim than an absolute source attribution based on 

the theory of global general uniqueness. Furthermore, in the case of a competent and careful 

comparison, it would be far less vulnerable to the charge of over-claiming. Judicial acceptance of 

such testimony need not await the admission of likelihood ratios from the automated systems 

described in Chapter 4. 

 

446 Aitken and Taroni, op. cit.; Evett, I., G. Jackson, J. Lambert, et al. “The Impact of the Principles of Evidence 

Interpretation on the Structure and Content of Statements.” Science & Justice, 40 (2000): 233. See also Cook, R., I. 

Evett, G. Jackson, et al. “A Model for Case Assessment and Interpretation.” Science & Justice, 38 (1998): 151. This 

table is reminiscent of Jeffrey’s scale for interpreting a Bayes factor. Jefferys, H. Theory of Probability, 3d ed. 

Oxford University Press, 1961. 447 See Hummel, K. and J. Gerchow, ed. Biomathematical Evidence of Paternity. 1982. Joint AMA-ABA 

Guidelines: Present Status of Serologic Testing in Problems of Disputed Parentage. Family Law Quarterly. 10 

(1976): 247.

448 Champod, C. “Friction Ridge Examination (Fingerprints): Interpretation of.” In Wiley Encyclopedia of Forensic 

Sciences edited by A. Moenssens and A. Jamieson, vol. 3, pp. 1508–11. J. Wiley & Sons, 2009. 449 Association of Forensic Science Providers. “Standards for the Formulation of Evaluative Forensic Science Expert 

Opinion.” Science and Justice, 49, no.3 (2009): 161 – 64.

450 Obviously, other phrases are defensible. The efforts to construct verbal scales are all somewhat arbitrary, both 

regarding the end points of the intervals and the choice of the words to describe them. Aickin, M. and D. Kaye. 

“Some Mathematical and Legal Considerations in Using Serologic Tests to Prove Paternity.” Inclusion Probabilities 

in Parentage Testing, 53 (1983): 167.
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Nevertheless, the strength-of-evidence approach is easier to use when more objective estimates 

of likelihoods can be computed, and statistical models to estimate likelihood ratios for fingerprint 

evidence have been developed. They have the potential to replace rigid, categorical opinions 

with more finely graded, numerical expressions of the probative value of the evidence (see 

Chapter 4). Some experts favor directly presenting the numerical value of the likelihood ratio to 

the jury, as is done in some DNA cases.451 Others have proposed comparing the likelihood ratio 

derived from the latent and exemplar in the case at hand to simulated ratios for pairings of the 

latent print with unrelated exemplars.452 The strength of the evidence then can be stated as the 

proportion of known cases with a lower likelihood ratio than that for the case at hand. For 

instance, the prosecution could point out that the likelihood ratio is higher than it is for 75% of 

cases in which two prints came from the same finger; the defense could reply that the same ratio 

was lower than it is for 25% of cases in which the prints came from the same finger.453

Of course, for numerical likelihood ratios to be admissible as evidence, the models must be 

adequately validated and accepted in the scientific community, and the courts must be persuaded 

that expressing the strength of evidence in the form of a likelihood ratio is not too confusing for 

juries.

454 The same concerns were raised with the presentation of likelihood ratios in DNA cases, 

and this form of testimony has been admitted in that area.455 

6.7.6 Describing the Significance of a Match: Posterior Probabilities

One argument for using the likelihood ratio to grade the strength of the evidence comes from a 

basic formula of probability theory known as Bayes’s rule (see Chapter 1). The formula 

describes the impact of an item of evidence on the odds that a proposition is true. It states that the 

odds in favor of the proposition are its prior odds adjusted (multiplicatively) by the likelihood 

ratio: posterior odds = likelihood ratio × prior odds. For example, if, before considering a 

fingerprint match to a suspect, it is assumed that the odds that the suspect left the latent print are 

1 to 300 million (roughly the size of the U.S. population), then, for a match with a likelihood 

ratio of 1 billion, the posterior odds that the suspect is the source is 109 × 1/(3 × 106) = 333:1. 

 

451 See Kaye, The Double Helix and the Law of Evidence, 2010, op. cit. 452 Gill, P., J. Curran, C. Neumann, et al. “Interpretation of Complex DNA Profiles Using Empirical Models and a 

Method to Measure Their Robustness.” Forensic Science International, 2 (2008): 9.

453 See, e.g., Morrison, G. “Measuring the Validity and Reliability of Forensic Likelihood-Ratio Systems.” Science 

& Justice, 51 (2011): 91 – 98. Some researchers have suggested that Tippett plots could be used to compute such 

proportions. Such plots express the cumulative distribution function of the log-likelihood ratio. Tippett, C., V. 

Emerson, F. Lawton, et al. “The Evidential Value of the Comparison of Paint Flakes from Sources Other Than 

Vehicles.” Journal of the Forensic Science Society, 8 (1968): 6. On the use of such plots in other forensic 

disciplines, see Evett, I. and J. Buckleton. “Statistical Analysis of STR Data.” Advances in Forensic Haemogenetics, 

6 (1996): 79; Srihari, S., C. Huang, and H. Srinivasan. “On the Discriminability of the Handwriting of Twins.” 

Journal of Forensic Science, 53 (2008): 430. For an example of Tippett plots for fingerprint analysis, see Egli, N., 

C. Champod, and P. Margot. “Evidence Evaluation in Fingerprint Comparison and Automated Fingerprint 

Identification Systems—Modelling Within Finger Variability.” Forensic Science International, 167 (2007): 189–95.

454 There have been various studies of the manner of communicating evidence in DNA cases. E.g., Nance, D. and S. 

Morris. “Juror Understanding of DNA Evidence: An Empirical Assessment of Presentation Formats for Trace 

Evidence with a Relatively Small Random-Match Probability.” Journal of Legal Studies, 34 (2005): 395. However, 

no study has included the use of likelihoods. Kaye, D., V. Hans, B. Dann, et al. “Statistics in the Jury Box: How 

Jurors Respond to Mitochondrial DNA Probabilities.” Journal of Empirical Legal Studies, 4 (2007): 797. 455 Kaye, The Double Helix and the Law of Evidence, 2010, op. cit.; cases cited Kaye, Bernstein, and Mnookin, op. 

cit. 
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Computations of this type have been introduced into court, primarily in parentage testing cases 

arbitrarily using prior odds of one-to-one. In other areas, courts in America and England have 

been less accommodating.456 There are obvious problems in defining the prior probability 

distribution. Assuming that everyone in the U.S. could have committed a particular crime, as in 

the example above, is plainly unrealistic. 

6.7.7 Describing the Significance of a Match: No Inference

When the distinguishing features of trace evidence are extremely rare, the evidence is highly 

probative—a particular set of features is many times more probable when the unknown trace 

sample and the known sample have a common source than when they do not. But for most 

identification technologies, scientific research to quantify the rarity of the set of identifying 

features is not feasible or available. Examples include hair morphology, compositional analysis 

of bullet lead, handwriting, and toolmarks. Analysis of these characteristics is surely informative, 

but it is difficult to provide a sharp estimate of probative value because of the absence of a 

typology of features that lends itself to estimates of population frequencies and the inability to 

compute a likelihood ratio from public data. In this situation, analysts in some fields do not even 

venture an opinion about the significance of the similarities they detect. Thus, in microscopic 

hair comparisons, unadorned “consistent with” testimony is the norm. In State v. McGrew,

457 for 

example, the hair examiner testified as follows: 

Court: In regard to the examination. It is simply a physical, visual examination of 

the hair. 

Analyst: Yes sir. 

Court: You simply say that one hair looks like another one or it doesn’t look like 

another one. 

Analyst: I say it’s sufficiently similar to have come from that person or it is 

dissimilar. 

Court: And if you say that it ... [is] similar to come from that person ... that 

doesn’t mean that it comes from that person. 

Analyst: It just simply means that it could have come from that person. 

Court: And you do not know the statistical percentages of how many people 

would have similar hair? 

Analyst: There are no statistics. It’s hard to say.458 

Similar testimony appears in some cases involving tests for the concentration of elements in 

bullet fragments and bullets found in a defendant’s possession.459

Some courts have followed this no-inference approach in cases involving the comparisons of 

documents and toolmarks.460 In United States v. McVeigh461 and United States v. Nichols,

462

 

456 The case law is analyzed in Kaye, Bernstein, and Mnookin, op. cit., § 12.8.5.

the 

457 State v. McGrew, 682 N.E.2d 1289 (Ind. 1997).

458 Ibid., p. 1291. 459 Cases are cited in National Academy of Sciences, National Research Council, Committee on Scientific 

Assessment of Bullet Lead Elemental Composition Comparison. Forensic Analysis: Weighing Bullet Lead Evidence. 

National Academies Press, 2004, pp. 91 – 94.
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government sought to show that a padlock at a quarry from which explosives were stolen had 

been opened by drilling with a drill bit found in Nichols’s home. In the former case, an FBI 

toolmark examiner testified that “this drill bit produced marks that were contained in the 

padlock.” In the latter case, when the same witness testified that he had attempted to “determine 

whether or not that drill bit made the impressions contained on that lock cylinder,” the district 

court struck the testimony “because what is permitted here is to show [only] what he saw through 

the microscope and the comparison microscope and then with his experience and training the 

similarities that he pointed out.” Thus, the toolmark examiner was allowed to testify to the 

marks, but no more than that. Similarly, a few courts confined testimony to comparing features 

in handwriting cases and, for a brief moment, in a fingerprint case.463 

A slight enhancement to pure “consistent with” testimony is a statement that “the probability of a 

match is greater if the bullets came from the same CIVL [compositionally indistinguishable 

volume of lead] than if they came from different CIVLs, and the odds that the bullets came from 

the same CIVL are greater with the matching evidence than without it.”464 In other words, the 

expert can report that the likelihood ratio is greater than one, but not how much greater. 

Although the forensic examiners’ experience suggests that the failure to exclude a suspect based 

upon the evidence is relevant, the jury has no experience of its own with which to judge how 

probative the findings are. Hair and toolmarks, for example, do differ from one instance to 

another,465 but it is difficult for the jury to know what to make of testimony that the defendant 

(or the material in the defendant’s possession) is consistent with the evidence collected at the 

crime scene.

466 Nonetheless, compared to complete exclusion of the match, this truncated 

presentation makes sense when it is known that the similar characteristics show substantial 

variation in the population and when an untutored jury is not likely to overestimate the 

variability.467 Thus, one court recently limited a latent print examiner to explaining the basis for 

a conclusion that “the latent fingerprint ... is consistent with the known print” by describing “the 

specific characteristics and markers in the prints” and adding that “based on his experience, 

certain markers are more common or less common.”468 

The details of fingerprints are extremely variable,469

 460 Kaye, Bernstein, and Mnookin, op. cit. 

 but those who question the premises of 

universal individualization would still object that even with no-inference testimony, the jury will 

overvalue the finding of a match. At the other pole, those who believe that a latent print can

461 No. 96-CR-68 (D. Colo. May 5, 1997) (transcript). 462 No. 96-CR-68 (D. Colo. Nov. 10, 1997) (transcript).

463 See, e.g., Mnookin, J. “The Courts, the NAS, and the Future of Forensic Science.” Brooklyn Law Review, 75, no. 

4 (2010): 1209. 464 NAS, NRC, Committee on Scientific Assessment of Bullet Lead Elemental Composition Comparison, op. cit., p. 

97.

465 Vanderkolk, J. Forensic Comparative Science: Qualitative Quantitative Source Determination of Unique 

Impressions, Images, and Objects. Academic Press, 2009.

466 Kaye, Bernstein, and Mnookin, op. cit. 467 Kaye, D. “The NRC Bullet-Lead Report: Should Science Committees Make Legal Findings?” Jurimetrics 

Journal of Law, Science, and Technology, 46 (2005): 91. 468 United States v. Zajac, No. 2:06-cr-00811 CW (D. Utah Sept. 16, 2010). 

469 E.g., Stoney, 2001, op. cit., p. 327.
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match only a single individual in the history of life on Earth would object that the absence of 

testimony to that effect deprives the jury of useful information.

In sum, the existing practice of latent print experts is to provide a firm opinion regarding whether 

a named individual is the source of a questioned print (either a universal individualization or an 

exclusion) or to give no opinion (by stating that the unknown impression is insufficient for a 

definitive comparison or that the comparison is inconclusive). But other ways to describe the 

possible association include statements about the strength of the evidence (the likelihoods) or the 

posterior probability. With appropriate data and validated modeling, such statements could be 

quantitative (see Chapter 4), but less precise qualitative descriptions of the strength of the 

evidence or the source probability also are possible. If expert knowledge permits opinions that a 

latent print came from a single individual and could not have come from anyone else in the 

world then, a fortiori, it supports opinions such as the following: it is unlikely that the print came 

from anyone else in a particular locale, it is much more likely to observe such similar prints from 

the same source than from different people, and the similarities in the prints support the 

prosecution’s hypothesis that the defendant is the source of the questioned print much more than 

they support the defendant’s hypothesis that they originated from different fingers.470 Given the 

current state of scientific and professional knowledge, however, it is best to avoid testimony 

based on the theory of global general uniqueness. Recommendation 3.7, that examiners not 

testify to an identification to the exclusion of all other individuals in the world, requires other, 

more conservative methods for conveying the probative value of a match. For that reason, this 

chapter identifies a broad spectrum of alternatives. The Working Group did not reach a 

consensus on which of these alternatives to universal-individualization testimony is best. 

6.8 Internal Review of Reports and Testimony

Chapters 4 and 5 emphasize the role of forensic scientists and examiners in communicating their 

findings to a variety of audiences, including criminal investigators, lawyers, and judges and 

juries. The recommendations include practices to facilitate the accurate and fair transmission of 

forensic investigations to these groups. The final recommendation is that a system be instituted 

to monitor the reports and testimony of practitioners. Performance reviews can ensure that the 

latent print unit’s policies for reporting and testifying are followed and can provide feedback to 

sustain and improve performance of these tasks. 

 

470 Even the current terminology of identification, exclusion, or inconclusive to describe the outcome of the 

Evaluation phase of ACE-V could be redefined using the concept of relative likelihood. For example, the definition 

of these terms in the first two sample reports in the Appendix to Chapter 5 could be rephrased as follows: 

Evaluation is the formulation of a conclusion based upon the information gathered during analysis and 

comparison. The evaluation can result in three outcomes: (1) an exclusion is an opinion that the level of 

disagreement in comparable areas is far more likely to be observed if the two prints did not originate from the 

same source than if they came from the same finger; (2) an identification is an opinion that the level of 

agreement in comparable areas is far more likely if the two prints originated from the same finger than if they 

came from different sources; or (3) an inconclusive result occurs when the information in comparable areas is 

inadequate for an identification or an exclusion.
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Recommendation 6.4: An agency that employs latent print examiners should establish 

requirements and guidelines for reporting, documentation, and testimony. The agency 

should review a sample of every examiner’s case reports, documentation, and testimony 

and affidavits at least annually to verify compliance with these requirements and 

guidelines.

SWGFAST and the FBI give similar advice, but their recommendations allow a survey form and 

statements from court officials to substitute for direct observation of live, recorded, or 

transcribed testimony.471 Presumably “court officials” means judges or lawyers, but review by 

laboratory managers and accrediting bodies as part of periodic inspections or in response to 

complaints from lawyers or their clients would be more appropriate to identify adherence to 

professional canons and organizational policies. 

6.9 Summary

This chapter describes the nature and role of expert testimony, pretrial communications between 

experts and lawyers, and the legal and ethical principles applicable to expert testimony. It 

considers the admissibility of different types of testimony about the possibility of erroneous 

identifications or exclusions. It also presents a spectrum of conceivable modes of conveying 

expert knowledge and findings about the possible association between a friction skin impression 

and its source. These range from a bare description of the relevant similarities, to statements 

about the strength of evidence (likelihoods), to outright conclusions about the source (source 

attributions or probabilities). Finally, the chapter discusses quality assurance and control for 

testimony.

 

471 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Quality Assurance Guidelines for 

Latent Print Examiners. Guideline 5.5.1, Version 3.0. Scientific Working Group on Friction Ridge Analysis, Study 

and Technology, September 2006; Peterson, Dreyfus, Gische, et al., op. cit. 
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Chapter 7: A Systems Approach to the Work Environment 

140 

Chapter 7: A Systems Approach to the Work Environment

Introduction and Scope

The environment in which latent print examiners work encompasses physiological and cognitive 

factors; management and leadership culture, communications, and collaboration opportunities; 

and the physical workspace. Well-designed work environments can improve productivity, 

increase user satisfaction, and reduce the risk of errors and injuries. Conversely, poorly designed 

environments contribute to poor performance. When an error occurs, most people tend to blame 

other humans rather than to consider the design, environmental working conditions, or 

management culture of the total system.472 Yet errors are often the consequence of an entire 

system.473 

A study of human factors examines human operators’ physical and psychological needs, 

capabilities, and limitations in both normal and emergency operations. A thorough analysis of 

workstations, job demands, mental workload, organizational characteristics, training needs, and 

supervisory systems is necessary to facilitate and enhance performance. Large-scale disasters, 

such as the accidents at the Three Mile Island and Chernobyl nuclear power plants, the Bhopal 

pesticide plant, and the Challenger space shuttle dramatically highlight the need for such 

analyses.

474 

Figure 7.1 sketches an example of a human factors framework that, if not properly understood, 

can lead to adverse events. This chapter addresses issues displayed in Tiers 1–3 of the figure and

analyzes the latent print examiners’ work environments to identify factors that could affect their 

performance. It enumerates the factors that contribute to an effective latent print analysis work 

environment, and it describes the anatomical, physiological, and psychological aspects of latent 

print examiners in their environment. It also suggests ways for managers to reduce injuries and 

errors; to increase productivity, efficiency, and effectiveness; and to improve the comfort of 

latent print examiners.

 

472 Luthar, S., D. Cicchetti, B. Becker. “Research on Resilience: Response to Commentaries.” Child Development, 

71, no. 3 (2003): 573. 473 Hopp, P., C. Smith, B. Clegg, et al. “Interruption Management: The Use of Attention-Directing Tactile Cues.” 

Human Factors, 47 (2005): 1; National Academy of Sciences, Institute of Medicine, Committee on Quality of 

Health Care in America. To Err Is Human: Building A Safer Health System. National Academies Press, 1999; 

Chignell, M. and J. Waterworth. Multimedia, Handbook of Human Factors and Ergonomics. 2nd ed. John Wiley & 

Sons, 1997; Bagot, G. “Ergonomics in the Laboratory Environment.” Nursing Management, 25 1994): 50; Henning, 

R., P. Jacques, G. Kissel, et al. “Frequent Short Rest Breaks From Computer Work: Effects on Productivity and 

Well-Being at Two Field Sites.” Ergonomics, 40 (January 1997): 78; Ezzelle, J., I. Rodriguez-Chavez, J. Darden, et 

al. “Guidelines on Good Clinical Laboratory Practice: Bridging Operations Between Research and Clinical Research

Laboratories.” Journal of Pharmaceutical and Biomedical Analysis, 46 (January 2008): 18; Grogan, E., R. Stiles, D. 

France, et al. “The Impact of Aviation-Based Teamwork Training on the Attitudes of Health-Care Professionals.” 

Journal of the American College of Surgeons, 199 (December 2004): 843. 474 Shrivastava, P., I. Mitroff, D. Miller, et al. “Understanding Industrial Crises.” Journal of Management Studies, 

25, no. 4 (1988): 285.
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Chapter 7: A Systems Approach to the Work Environment 

141 

Figure 7.1: A human factors framework475

 

475 Image adapted from Henriksen, K., E. Dayton, M. Keyes, et al. “Understanding Adverse Events: A Human 

Factors Framework.” In Patient Safety and Quality: An Evidence-Based Handbook for Nurses edited by Ronda G. 

Hughes. Agency for Healthcare Research and Quality, 2008.
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7.1 Human Factors and the Work Environment

The study of human factors focuses on 

the interaction between human and 

products, decisions, procedures, 

workspaces, and the overall environment 

encountered at work and in daily 

living.477 As the Institute of Medicine 

explains, most factors that give rise to 

preventable adverse events are 

systemic.478 These events are not just the 

result of isolated or idiosyncratic 

behavior. 

Often, people are required to work in 

poorly designed environments that have 

not had human strengths and limitations 

incorporated into the design process. A 

work environment can be disruptive, 

stressful, and unsafe, leading to 

unnecessary fatigue. It is well understood 

in various industries, including 

“high-risk industries” such as the 

medical profession, that a physical work 

environment purposefully designed for 

the nature of the work to be performed 

will result in improved efficiency and 

productivity.479 Proper design of the 

physical workspace, standardization of 

facility systems and equipment, 

ventilation systems for pathogen control, 

appropriate and adjustable lighting, and 

noise reduction are necessary for 

lowering stress and improving 

performance. 

 

476 Meshkati, N. “Human Factors in Large-Scale Technological Systems’ Accidents: Three-Mile Island, Bhopal, 

Chernobyl.” Organization & Environment, 5, no. 2 (June 1991): 133–54.

477 Sanders, J. and E. McCormick. Human Factors Engineering and Design. McGraw-Hill 

Science/Engineering/Math, 1993.

478 NAS, Institute of Medicine, op. cit. 479 Ulrich, R., X. Quan, C. Zimring, , et al. “The Role of the Physical Environment in the Hospital of the 21st 

Century: A Once-In-A-Lifetime Opportunity.” In Designing the 21st Century Hospital Project, The Center for 

Health Design. May 2005. See also Chapanis, A., W. Garner, and C. Morgan. Applied Experimental Psychology: 

Human Factors Engineering Design. Wiley, 1985 (“It is in the system design of the work environment as a whole 

where efficiencies and productivity will be realized.”).

Box 7.1: Three Mile Island Accident

The Three Mile Island nuclear power plant accident is the 

most investigated accident in the history of the commercial 

nuclear industry. Because human factors considerations 

were not included in the design of the control room, 

operators experienced problems locating or accessing the 

tools and information they needed. 

• System controls were not located near the 

instruments that displayed the condition of the 

system. For example, operators could not view the 

indicator display for the high-pressure system while 

operating the throttle valve to adjust pressure.

• Some instruments looked very similar and were 

located near one another but controlled different 

functions. 

• Other instruments were difficult to read due to glare 

from poor lighting or obstruction by other controls. 

• Throughout the control room, there was no 

consistent meaning of indicators (such as lights and 

alarms) or function of instruments (such as levers 

and knobs) between controls. 

• At the time of the accident, operators in the control 

room heard 3 alarms and saw more than 1,600 

blinking lights.

• Operators had not received adequate stress training 

to enable them to cope with such a large-scale, 

multiple systems failure.476 

These design problems illustrate the range of situations and 

conditions that the human factors approach should consider. 
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Sound workplace design begins with a thorough understanding of user requirements. Since the 

early 1970s, architects have used methods, similar to function and task analysis techniques 

developed by human factors practitioners, that inventory all of the activities that will be 

performed in an environment to ensure that the appropriate requirements are defined and 

implemented. 480

The International Organization of Standardization’s standard on ergonomic requirements (ISO 

9241) defines usability as “the extent to which a product can be used by specified users to 

achieve specified goals with effectiveness, efficiency, and satisfaction in a specified context of 

use.” 481 

In its narrowest sense, usability involves the evaluation of a system; in its broadest sense, 

usability involves users throughout the system lifecycle (i.e., through the requirements definition, 

design, development, and evaluation phases).482 The most successful designs involve users 

iteratively starting with the early stages of design to develop and refine the designs.483 This usercentered design process involves:

• Early focus on users, their tasks, and their environments; 

• Active involvement of users; 

• Appropriate allocation of function between user and system; 

• Incorporation of user-derived feedback into the design; and 

• Iterative design, where a prototype is designed, tested, and modified. 484 

By contributing to the design of a usable work environment, latent print examiners can enhance 

ease of use, improve user performance and satisfaction, and reduce system complexity and 

support and training costs. The goal of designing a work environment following usability 

principles is to improve performance, to increase accuracy, to decrease time to prepare latent 

prints for search, to decrease support and training costs, and to increase user acceptance. 

Appendix A provides additional information on user-centered design.

Recommendation 7.1: A structured approach that involves users throughout the entire 

design and implementation process should be followed when designing technology 

systems and the physical work environment. In addition, forensic service providers 

should perform usability testing to optimize user performance and user satisfaction 

before deployment.

 

480 Zimring, C., M. Rashid, and K. Kampschroer. “Facility Performance Evaluation (FPE).” Whole Building Design 

Guide. National Institute of Building Sciences. 2010. 481 International Organization for Standardization. Ergonomic Requirements for Office Work with Visual Display 

Terminals (VDTs)—Part 11: Guidance on Usability, ISO 9241-11:1998. International Organization for 

Standardization, 1998.

482 U.S. Department of Commerce, National Institute of Standards and Technology. Usability & Biometrics: 

Ensuring Successful Biometric Systems. National Institute of Standards and Technology, June 11, 2008. 483 Nielsen, J. Usability Engineering. Morgan Kaufmann, 1993. 484 Maguire, M. “Context of Use Within Usability Activities.” International Journal of Human-Computer Studies, 

55 (2001): 453–83
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7.2 A Human Factors Approach to Latent Print Practices

A truly usable work environment considers the needs of the latent print examiners throughout the 

design, development, and evaluation process. This process requires environmental designers to 

define the context of use (including the users’ individual characteristics), to define the user’s and 

the organization’s requirements for the space, to develop a design solution to meet those 

requirements, and to conduct user evaluations to ensure that the environment is meeting all 

requirements as efficiently as possible.485

7.2.1 Methodology 

A human factors approach focuses on users’ needs and expectations and integrates direct user

feedback throughout the design process. To achieve this goal, human factors experts may 

observe or interview users to better understand their needs, work processes, and the 

methodologies they apply in completing their work. 

To better understand latent print examiners’ methodologies and processes as well as their 

environments, the National Institute of Standards and Technology (NIST) Visualization and 

Usability Group interviewed a total of 16 latent print examiners from the Federal Bureau of 

Investigation (FBI), Department of Defense, Central Intelligence Agency, U.S. Secret Service, 

and the New York State Department of Criminal Justice Services. Following these initial 

interviews, the team spent 2 days observing latent examiner teams at the Maryland State 

Forensic Laboratory, FBI, and United States Immigrant Status Indicator Technology (US-VISIT) 

while they performed their usual work tasks in their usual work environments. 

After approximately 21 hours of interviews and 32 hours of observation sessions, the team 

discovered that each organization uses a well-defined process to decide who performs which 

task, how they complete each task, and how they transition between tasks. The agencies also 

require specific documentation for each task and utilize procedures for transitioning the 

documentation through the steps. Each organization and its examiners are very comfortable with 

their processes and, to some extent, proud of them. These processes are tailored or unique to 

each organization. 

The physical layout of each facility is very different and seems to depend on the size of the 

organization. Of the surveyed organizations, many have a separate workspace for the chemical 

processing of the evidence. Most examiners have a small desk, and in the larger organizations, 

the examiners’ desks are in small cubicles. Most of the desks are covered with stacks of paper, 

including photos and printouts. Printing and scanning are consistently important activities, and 

many desks include printers and scanners. The impression from all of the interviews is that the 

organizations are “paper bound.” Structured forms seem to be essential to all organizations. 

Some organizations use “shops” or task-specific stations. For example, examiners use one 

workstation exclusively for case management, another for accessing the state automated 

 

485 International Organization for Standardization. Human-Centered Design Process for Interactive Systems, ISO 

13407:1999. Withdrawn, 1999. Revised by International Organization for Standardization. Ergonomics of HumanSystem Interaction—Part 210: Human-Centered Design for Interactive Systems, ISO 9241-210:2010. International 

Organization for Standardization, 2010.
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fingerprint identification system (AFIS) database, another for accessing the local AFIS database, 

and another for linking to the FBI’s Integrated AFIS database. The examiner moves the physical 

evidence and associated documentation from station to station when working through the steps 

of the process. 

In short, there is no one specific or even general solution to the design and specification of the 

laboratory environment. Design specifications must be tailored to individual departments. 

However, although each organization has a somewhat different process for examining latent 

prints, the NIST usability team recognized general similarities. 

Common Features of the Manual Examination Process

Examiners use a manual process when the latent prints are not of AFIS quality or when there is a 

known suspect and it is necessary to eliminate victim prints. The manual examination process 

generally includes the following steps: 

1. Prepare package (includes lift cards and latent photos); 

2. Confirm package contents; 

3. Assign card numbers to lift cards and latent photos; 

4. Determine suitability of prints; 

5. Mark latent print with symbols to document possible anatomical regions and print 

orientation; 

6. Pull exemplar prints for comparison; 

7. Begin comparison process on suitable prints; 

8. Document results of the comparison; and 

9. Conduct verification and technical review. 

Common Features of the AFIS Process

When using AFIS, the examiners at the agencies studied generally perform the following steps: 

1. Select a latent print to search; 

2. Scan the print into the system or obtain a digital print; 

3. Process the digital image in external image processing software; 

4. Enter case data; 

5. Encode unique ridge characteristics; 

6. Set search criteria; 

7. Launch AFIS search; 

8. Examine the resulting candidate images; 

9. Conduct verification and technical review; and 

10. Document additional case data. 

7.2.2 Work Environment Usability Goals 

Environment designers, including software developers, should apply the user-centered design 

process to identify the requirements of the organization. Then, they should translate usability 

goals into measurable objectives for the latent print examiner environment. Environment 

designers can use these metrics to assess an environment’s usability. Examples of commonly 

used usability criteria include: 
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• Success rate (effectiveness): Can users successfully work in the environment? 

• Time on task (efficiency): Can users perform their tasks quickly in the environment? 

• Time to learn a task (learnability): How long does it take a user to learn a product or the 

system?

• Memorability: Can users remember how to use the system, and does it aid the user in 

reducing the potential for error? 

• Satisfaction: Are users comfortable in the environment?486 

The tables and additional information in Appendix A provide a short description of each of these 

usability goals and include some questions for environment designers to consider. 

7.2.3 Design Approach for Latent Print Examination Environment

A user-centered design process involves users throughout the product lifecycle. When used for 

latent print examiners, the approach includes: 

• Identifying the types of users who will be using the workspaces (e.g., latent print 

examiners, forensic specialists, lab managers);

• Defining the context of use, including the operational environment (physical 

environment), user characteristics (anthropometrics), tasks, and social environment; 

• Determining the user and organizational requirements, including business requirements, 

visual requirements, environmental requirements, and technical requirements;

• Developing the design solution, including the physical space (e.g., lighting, air quality, 

workspace, and noise), system design, and user interface; and 

• Conducting an evaluation, including usability testing of the visual and environmental 

requirements of latent print examination tasks. 487

The design process reflects the fact that all aspects of the workflow and environment are 

interrelated. An examination of a forensic service provider’s process map and an independent 

detailed analysis of how work is actually performed can reveal procedures that can lead to error. 

Consideration should be given to the nature and demands of the work, the tools and technologies 

used, the physical environment, and the organizational conditions, such as the level of 

communication and collaboration among the individuals who perform the work or use the end 

product. These elements are interdependent; a change in one work element has implications for 

the other elements.

7.3 Observations of Impact Factors

Latent print comparisons require concentration. The environment in which an examiner works 

influences his or her ability to maintain the necessary level of attentiveness. It is not enough to 

consider only how the examiner will fit and function in the space from a physical perspective. 

 

486 Nielsen, op. cit. 487 Maguire, op cit.; ISO 13407:1999 (withdrawn), op. cit.
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Attention to the impact that the physical workspace may have on cognitive processes, including 

attentiveness, awareness, perception, reasoning, and judgment, is critical. 

The following factors, which are discussed below, could influence the latent print examiner’s 

work: occupational health and safety; medical surveillance; workstation configurations; software 

applications and systems; screen interfaces; the placement, type, and format of instructions, 

assistance, and help documentation; air quality, including temperature and humidity; lighting; 

noise; interruptions or distractions; location of the workstation; and stress. 

7.3.1 Occupational Health and Safety Issues 

Occupational health and safety within the forensic laboratory system is mandatory. However, 

workplace safety is not always a conscious or primary concern of latent print examiners. They 

are generally busy with casework, trial preparation, proficiency testing, and other concerns. 

The latent print examiner has the potential to come in contact with most types of physical 

evidence submitted to the forensic service provider. Hazards may originate from the item of 

evidence through sharp edges, chemical and biological contamination, or other hazards; the 

evidence may also include firearms, ammunition, or explosives. Of special concern are items 

contaminated or stained with human bodily fluids, which may contain blood-borne pathogens. 

Additionally, latent print processing may employ hazardous chemicals, particulates, and intense 

light sources. Chemical exposure is a serious concern. During the processing of latent prints, 

examiners could be exposed to fumes, dust, and toxic or caustic chemicals. Additionally, postanalysis protection of certain latent examinations on physical evidence must be employed to 

eliminate the chance of contamination to persons in the evidence chain of possession. This 

typically is accomplished by storing the evidence in a container that prevents trace reagent 

exposure. 

An accident can have an effect on an examiner’s efficiency and performance quality. For 

example, a malfunctioning fume hood could expose the examiner to vapors that impair

performance. Likewise, an employee who slips and falls in the work area could sprain a muscle 

or fracture a bone, requiring medical attention and possibly resulting in long-term pain or limited 

range of motion or dexterity. An injured examiner may have to compensate during the 

examination procedure, and this could affect the results. 

Many standards are relevant here, including Occupational Safety and Health Administration 

(OSHA) Standards, 29 Code of Federal Regulations (CFR) 1910, 1960, 1904; OSHA’s

bloodborne pathogens standard (29 CFR 1910.1030); and OSHA’s requirements for personal 

protective equipment (29 CFR, 1910 Subpart I). Guidelines for safety committees are found in 

29 CFR 1960. Airborne contaminant limits are described in 29 CFR 1910.1000. 
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7.3.2 Medical Surveillance

Vision testing is important for latent print examiners. Studies indicate that age, environment, and 

task-specific activity can cause vision to deteriorate.488 It is not clear which tests are the most 

appropriate for evaluating vision challenges for latent print analysis.489 Table 7.1 indicates the 

American Optometric Association’s recommended frequency for eye examinations for adult 

patients. Individuals at risk “include those with diabetes, hypertension, or a family history of 

ocular disease (e.g., glaucoma, macular degeneration) ... ; those working in occupations that are 

highly demanding visually or eye hazardous; those taking prescription or nonprescription drugs 

with ocular side effects; those wearing contact lenses; and those with other health concerns or 

conditions.”490 

Examination Interval 

Patient Age Asymptomatic (Risk Free) At Risk

18 to 40 years Every 2 years Every 1 to 2 years or as recommended 

41 to 60 years Every 2 years Every 1 to 2 years or as recommended 

61 years and older Every 1 year Every 1 year or as recommended

Table 7.1: Recommended eye examination frequency for adult patients491

Various tests are available to examine visual performance. For example, the Snellen chart is 

often used to measure visual acuity. Likewise, the Amsler Grid, a square grid with a black dot in 

the center, is used to detect changes in the central visual field. Proper use of the grid can detect 

very subtle changes in vision caused by a small amount of fluid under the retina. 

Contrast sensitivity tests check for the ability to differentiate between light and dark. Regular use 

of the Hamilton Veale contrast sensitivity test, illustrated in Figure 7.2, is one effective way to 

 

488 Sunness, J., G. Rubin, C. Applegate, et al. “Visual Function Abnormalities and Prognosis in Eyes with AgeRelated Geographic Atrophy of the Macula and Good Visual Acuity.” Ophthalmology, 104 (1997): 1677.; Sunness, 

J., G. Rubin, A. Broman, et al. “Low Luminance Visual Dysfunction as a Predictor of Subsequent Visual Acuity 

Loss from Geographic Atrophy in Age-Related Macular Degeneration.” Ophthalmology, 115 (2008): 1480; Midena, 

E., A. Degli, M. Blarzino, et al. “Macular Function Impairment in Eyes with Early Age-Related Macular 

Degeneration.” Investigative Ophthalmology & Visual Science, 38 (February 1997): 469; Abramov, I. and J. 

Gordon. “Color Vision Panel Tests: A Metric for Interpreting Numeric Analytic Indices.” Optometry & Vision 

Science, 86 (2009): 146; Montés-Micó, R. and T. Ferrer-Blasco. “Contrast Sensitivity Loss in the Peripheral Visual 

Field Following Laser in Situ Keratomileusis.” Journal of Cataract and Refractive Surgery, 33 (2007): 1120; Kon, 

C. and D. De Alwis. “A New Colour Vision Test for Clinical Use.” Eye (London, England), 10, pt. 1 (1996): 65-74. 489 Powers, M. “Paper Tools for Assessing Visual Function.” Optometry & Vision Science, 86 (2009): 613.; Bartlett, 

H., L. Davies, and F. Eperjesi. “The Macular Mapping Test: A Reliability Study.” BMC Ophthalmology, 10 (2005): 

18; Leat, S. and G. Woo. “The Validity of Current Clinical Tests of Contrast Sensitivity and Their Ability to Predict 

Reading Speed in Low Vision.” Eye (London, England), 11, pt. 6 (1997): 893; Witmer, M., C. Margo, and M. 

Drucker. “Tilted Optic Disks.” Survey of Ophthalmology, 10 (2010): 403; Barnhardt, C., S. Clock, B. Demmer, et al. 

“Color Vision Screening for Individuals with Intellectual Disabilities: A Comparison Between the Neitz Test of 

Color Vision and Color Vision Testing Made Easy.” Optometry, 77 (2006): 211; Isaac, D., M. Avila, and A. 

Cialdini. “Comparison of the Original Amsler Grid with the Preferential Hyperacuity Perimeter for Detecting 

Choroidal Neovascularization in Age-Related Macular Degeneration.” Optometry, 79 (2008): 397. 490 American Optometric Association. Comprehensive Adult Eye and Vision Examination. American Optometric 

Association, 2005.

491 Adapted from American Optometric Association, op. cit.
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monitor contrast sensitivity function over time.492 Forensic 

service providers should perform other vision tests regularly 

so that examiners know when they need to seek corrections to 

their sight to maintain high visual acuity. 

Recommendation 7.2: Forensic service providers 

should institute medical surveillance for examiners 

with respect to activities specific to friction ridge 

examination. Corrective measures should be taken 

when appropriate and recorded. The program should 

include a baseline visual examination followed by 

annual vision testing to detect vision deficiencies that 

may affect interpretation of the evidence. The federal government should support 

research to determine the most appropriate tests of visual function for friction ridge 

examiners. 

7.3.3 Workstation Configuration 

Workstation considerations include the physical location and 

design of the workstation as well as the desk height, counter 

height, and other spatial layout requirements. Latent print 

examinations require sufficient space for the latent prints, 

exemplars, documentation worksheets, magnifying glasses, 

pointers, writing instruments, and desktop task lighting. The 

space should permit the required materials to be laid out for the 

sequential process and to be accessible without undue attention 

or effort. Clutter is a potential source of frustration and error. 

Examiners experience physical problems, such as repetitive 

motion injuries, from a lack of ergonomic workstation design. 

Complicating this design issue is the fact that many examiners 

are required to share workstations across shifts. Inadequacies 

can include nonadjustable keyboards; awkward positioning of 

the mouse; chairs, desks, and monitors that are not adjustable to 

accommodate for different user heights; inadequate desk space for papers, work products, and 

equipment; insufficient leg and knee room under the desk; furniture that impedes equipment 

access; and lighting that cannot be adjusted for using magnifiers.

The working environment and user work posture are critical in preventing repetitive motion 

injuries. The impact of ergonomics on individual productivity in domains such as automobile 

manufacture, food processing, and healthcare is well documented.493

 

492 The Hamilton Veale contrast sensitivity chart should be used in conjunction with an Amsler Grid to detect visual 

function loss in all cases with macular degeneration.

 Good ergonomic designs 

493 Cocci, S., K. Namaisvayam, and P. Bordi. “An Investigation of Ergonomic Design and Productivity 

Improvements in Foodservice Production Tables.” Foodservice Research International, 16 (2005): 53; Kolich, M. 

and S. Taboun. “Ergonomics Modeling and Evaluation of Automobile Seat Comfort.” Ergonomics, 47, no. 8 (June 

Figure 7.3: An example of 

a poorly designed 

workstation

Figure 7.2: The Hamilton Veale 

contrast sensitivity test
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150 

increase output per worker and reduce errors, accidents, injuries, illnesses, training time, 

maintenance time, absenteeism, and turnover. Although no studies have focused on latent print 

examiners, there is no reason to believe that the results would not generalize from related 

occupations. 

At a minimum, an examiner’s workstation should have keyboard shelves that are adjustable to 

accommodate different heights; computer mice that can be repositioned; chairs that are 

adjustable for height, arms, and back support; desktops that have mechanisms for adjusting tilt 

and height; monitors that are adjustable both in height and user proximity; and a desk with 

sufficient workspace, legroom, and knee space. Applicable standards include ISO 9241-

302:2008.494

7.3.4 Software Applications and Systems

It is critical to include latent print examiners in the 

design of all solutions, especially technology 

solutions. Eliciting requirements from latent 

examiners and having them participate in usability 

testing is necessary to create successful and usable 

products and processes. The usability testing and 

evaluation process permits the user to provide data 

about what works and what does not. The iterative 

nature of the process allows changes to produce an 

optimized software application or solution. Too often, 

usability evaluations are carried out, if at all, only 

after a product has been designed, developed, and 

deployed. Applicable standards are ISO/IEC 9126,495

ISO 9241-210,496 and ISO/IEC 25062497

 22, 2004): 841–63; Stone, R. and R. McCloy. “Ergonomics in Medicine and Surgery.” BMJ, 328, no. 7448 (May 6, 

2004).

(software 

engineering, software product quality requirements 

and evaluation, and common industry format for usability test reports). 

494 International Organization for Standardization. Ergonomics of Human-System Interaction—Part 302: 

Terminology for Electronic Visual Displays, ISO 9241-302:2008. International Organization for Standardization, 

2008; International Organization for Standardization. Ergonomics of Human-System Interaction—Part 305: Optical 

Laboratory Test Methods for Electronic Visual Displays, ISO 9241-305:2008. International Organization for 

Standardization, 2008. Both of these standards replace the withdrawn International Organization for Standardization. 

Ergonomic Requirements for Work with Visual Displays Based on Flat Panels), ISO 13406:1999 (withdrawn). 

International Organization for Standardization, 1999. 495 International Organization for Standardization. Software Engineering—Product Quality, ISO/IEC 9126:2001. 

International Organization for Standardization, 2001.

496 International Organization for Standardization. Ergonomics of Human-System Interaction—Part 210: HumanCentered Design for Interactive Systems, ISO 9241-210:2010. International Organization for Standardization, 2010. 

Replaces the withdrawn standard ISO 13407:1999, op. cit. 497 International Organization for Standardization. Software Engineering—Software Product Quality Requirements 

and Evaluation (SQuaRE)—Common Industry Format (CIF) for Usability Test Reports, ISO/IEC 25062:2006. 

International Organization for Standardization, 2006.

Figure 7.4: An example of a poorly 

designed user interface
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7.3.5 Screen Interfaces

Poorly designed software interfaces were observed in some laboratories. For example, in Figure 

7.4, the color combination (i.e., red background with blue text) is difficult to read, causes 

eyestrain, and has the potential to increase errors. The applicable standards are ISO/IEC 9126,498

ISO 10075-2,499 ISO 9241-210,500; and ISO/IEC 14598.501

7.3.6 Instructions, Assistance, and Help 

Examiners work across disparate application interfaces, which can be confusing. Managers 

should place instructions of all types and formats in locations accessible and visible to employees. 

Posted instructions should include icons and font sizes that are large enough to see. Forensic 

service providers should also consider the best ways to present error feedback, assistance, and 

helpful information to examiners. Although the NIST team did not document instructional 

training process or online help functions, any instructions or help should follow human factors 

guidelines and standards. 

Online documentation, training, and help can be beneficial. Unfortunately, most of the current 

online documentation is little more than paper documentation displayed on a computer screen. 

Designers of online instruction and documentation should consider the delivery technique and 

should utilize indexes, searches, and other navigational tools, including text, graphics, and icons, 

to help users find relevant content.502 Research on both hard-copy and online documentation 

suggests that users seldom read the entire document.503 Learning styles also influence the user’s 

preference in accessing information.504 

Many icons used in instructions for examiners do not easily describe the tasks they represent. For 

some especially obscure icons, even pop-up label descriptions do not assist in comprehension.505

before launching the product. Applicable standards are ISO/IEC/IEEE 26512

Designers should use standard icons whenever possible and should conduct usability testing 506 and ISO/IEC 

11581.507

 

498 ISO/IEC 9126:2001, op cit. 

 

499 International Organization for Standardization. Ergonomic Principles Related to Mental Workload—Part 2: 

Design Principles, ISO 10075-2:1996. International Organization for Standardization, 1996.

500 ISO 9241-210:2010, op cit. 501 International Organization for Standardization. Information Technology—Software Product Evaluation, ISO/IEC 

14598:1999. International Organization for Standardization, 1999.

502 Moallem, A. “Usability of Software Online Documentation: A User Study.” HCI International, 1 (2003): 549.

503 Rettig, M. “Nobody Reads Documentation.” Communications of the ACM, 34 (1991): 19. 504 Kolb, D. Experiential Learning: Experience as the Source of Learning and Development. Prentice Hall, 1984;

Felder, R. “Reaching the Second Tier: Learning and Teaching Styles in College Science Education.” Journal of 

College Science Teaching, 23 (1993): 286. 505 Zammit, K. “Computer Icons: A Picture Says a Thousand Words. Or Does It?” Journal of Educational 

Computing Research, 23 (2000): 217. 506 International Organization for Standardization. Systems and Software Engineering—Requirements for Acquirers 

and Suppliers of User Documentation, ISO/IEC/IEEE 26512:2011. International Organization for Standardization, 

2001. Replaces the withdrawn standard I International Organization for Standardization. Information Technology—

Software User Documentation Process, ISO/IEC 15910:1999 (withdrawn). International Organization for 

Standardization, 1999. 
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7.3.7 Environmental Factors

Air Quality 

Air quality refers to the average or extreme temperature and humidity of the location along with 

any contaminants. It is often difficult to control air temperature and airflow, especially in open 

office spaces. Examiners’ movements between offices and the additional heat resulting from that 

movement complicate control over air quality. Fortunately, temperature can be controlled with 

some degree of accuracy depending on the building’s heating, ventilating, and air conditioning 

(HVAC) system. Indoor temperature affects comfort, perceived air quality, sick building 

syndrome symptoms, and performance.508 

Suboptimal ventilation rates and higher occupancy density are associated with lower work 

performance.509 Improved perceived air quality reduces the intensity of sick building syndrome 

symptoms and improves performance.510 Latent print unit managers should monitor the airflow

and temperature in all examiner workspaces and, if needed, should install desktop task or 

ambient conditioning systems or air purifying systems. The standards applicable to air quality are 

OSHA Section III Chapter 2 (general recommendations for indoor air quality problems including 

ventilation, air treatment, and source controls)511 and ISO 16814 (specifying methods to express 

the quality of indoor air suitable for human occupancy allowing several acceptable target levels 

of indoor air quality depending on local requirements, constraints, and expectations).512

Lighting

Examiners may experience vision problems, eyestrain, and injury with insufficient or 

inappropriate lighting. Placing monitors in front of windows increases glare. Glare from nonadjustable and non-directional lighting fixtures and lamps results in squinting. Inadequate levels 

of light for the task, inconsistent background luminosity, a lack of natural lighting, a lack of 

window fixtures to control natural light, as well as non-adjustable lamps for use during 

magnification all can cause glare. However, studies have found that a view out a window is 

associated with better worker performance, less fatigue, and better self-reported health 

 507 International Organization for Standardization. Information Technology—User System Interfaces and Symbols—

Icon Symbols and Functions, ISO/IEC 11581:2000. International Organization for Standardization, 2000. 508 Seppänen, O., W. Fisk, and Q. Lei. Effect of Temperatures on Task Performance in Office Environment. Helsinki 

Univ. of Technology, Laboratory of Heating, Ventilating, and Air-Conditioning, July 2006.

509 Federspeil, C., G. Lui, M. Lahiff, et al. “Worker Performance and Ventilation: Analyses of Individual Data for 

Call-Center Workers.” Indoor Air, 14 (2002): 41. 510 Wargocki, P., D. Wyon, J. Sundell, et al. “The Effects of Outdoor Air Supply Rate in an Office on Perceived Air 

Quality, Sick Building Syndrome (SBS) Symptoms and Productivity.” Indoor Air, 10, no. 4 (2000): 222–36; Fang, 

L., D. Wyon, G. Clausen, et al. “Impact of Indoor Air Temperature and Humidity in an Office on Perceived Air 

Quality, SBS Symptoms and Performance.” Indoor Air, 14, supp. 7 (2004): 74–81.

511 U.S. Department of Labor, Occupational Safety & Health Administration. OSHA Technical Manual, Section III, 

Chapter 2, Indoor Air Quality Investigation. Occupational Safety & Health Administration, 1999. 512 International Organization for Standardization. Building Environment Design—Indoor Air Quality—Methods of 

Expressing the Quality of Indoor Air for Human Occupancy, ISO 16814:2008. International Organization for 

Standardization, 2008.
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conditions.513 Higher levels of daylight illumination have a positive impact on attention span and 

short-term memory tests.514

Lighting conditions affect individual performance via the visual, circadian, and perceptual 

systems.515 The lighting conditions determine the capabilities of the visual system. The state of 

the circadian system (sleep-wake cycle) is influenced by the light-dark cycle. And the “message” 

delivered by the perceptual system is influenced by many factors, including light.516 Because the 

need for varying levels of light greatly affects examiners’ ability to complete their tasks quickly, 

efficiently, and correctly, managers and environment designers should take the following actions: 

• Place monitors away from windows to reduce glare and reflections; 

• Provide monitor anti-glare screens;

• Tilt the monitor screen to avoid reflections;

• Adjust screen or character background colors (e.g., black characters on a white screen 

will produce less glare than white characters on a blue background); 

• Use ceiling fixtures that provide controlled, indirect lighting; 

• Install adjustable light level switches;

• Install and use window blinds to control outside light; 

• Use task lights positioned to avoid shadows; 

• Provide optimal lighting for examiners using loupes; and 

• Reduce other brightness sources, such as glossy, reflective paints on walls or highly 

reflective work surfaces. 

Applicable standards include ISO 8995 (interior lighting, including workplace, emergency, and 

safety lighting).517

Noise

Noise interferes with worker performance.518

 

513 Collins, B. Windows and People: A Literature Survey, Psychological Reaction to Environments With and 

Without Windows. U.S. Dept. of Commerce, National Bureau of Standards, 1975; Kaplan, R. and S. Kaplan. The 

Experience of Nature: A Psychological Perspective. Cambridge University Press, 1989. 

 Noise can prevent workers from hearing signals 

and can interfere with a worker’s mental and physical condition. Indeed, noise can be a health 

hazard. It can produce serious physical and mental performance problems and psychological 

stress. Workers in departments with high noise levels have more disciplinary actions and 

absenteeism and less productivity. Noise also appears to affect the quality of work and accident 

514 Heschong Mahone Group. Windows and Offices: A Study of Office Worker Performance and the Indoor 

Environment – CEC PIER 2003. 2003.

515 Leslie, R. “Capturing the Daylight Dividend in Buildings: Why and How?” Building and Environment, 38, no. 2 

(February 2003): 381–85. 516 Boyce, P., C. Hunter, and O. Howlette. The Benefits of Daylight Through Windows. Lighting Research Center, 

Rensselaer Polytechnic Institute, 2003; Juslen, H. and A. Tenner. “Mechanisms Involved in Enhancing Human 

Performance by Changing the Lighting in The Industrial Workplace.” International Journal of Industrial 

Ergonomics, 35 (2005): 843. 517 International Organization for Standardization, Lighting of Work Places, ISO 8995:2002. International 

Organization for Standardization, 2002.

518 Morrison, W., E. Haas, D. Shaffner, et al. “Noise, Stress, and Annoyance in a Pediatric Intensive Care Unit.” 

Critical Care Medicine, 31, no. 1 (2003): 113; Topf, M. “Hospital Noise Pollution: An Environmental Stress Model 

to Guide Research and Clinical Interventions.” Journal of Advanced Nursing, 31 (2000): 520.
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rates.519 Although humans often adjust by ignoring noise, the ear does not stop processing 

sound.520 Distracting noise sources can range from overhead paging systems and equipment 

alarms to HVAC systems, plumbing, and other employees. 

In a majority of the organizations studied, the NIST team observed staff members playing music 

and having conversations that could be distracting. Materials that absorb sound, such as ceiling 

and wall materials and carpeting, can mitigate the impact of noise at a modest cost.521 Applicable 

standards are ISO 11201522 and OSHA 1910.523 

7.3.8 Distractions

Interruptions 

Interruptions of the examination process can introduce error. Interruptions can come from any 

number or sources, but the design of the workspace can mitigate some of them.524 Such 

interruptions can halt the examination process or can result in the examiner attempting to manage 

the interruption while continuing with the examination. After an interruption, an examination 

might not continue at the same point as it ended. 

Conversations are a common form of interruption. Research reveals that in only limited 

circumstances are people able to perform two tasks concurrently.525 Conversations actually 

demand a high level of cognitive processing to be attentive and to formulate a response. An 

examiner whose attention is diverted from the primary task becomes vulnerable to making a 

mistake.526

Latent print comparison workstations can be designed as an open space, a semi-private office, or 

a private office. In the open space or semi-private office design, the examiner is likely to be 

subject to unsolicited conversation either directed to him or overheard from others in the same 

area. In a majority of incidents involving cockpit crew errors studied by the National Aeronautics 

and Space Administration (NASA), the crews reported having been distracted by conversation at 

 

519 Noweir, M. “Noise Exposure as Related to Productivity, Disciplinary Actions, Absenteeism, and Accidents 

Among Textile Workers.” Journal of Safety Research, 15 (1984): 163; Muzammil, M., A. Khan, F. Hasan, et al. 

“Effect of Noise on Human Performance Under Variable Load in a Die Casting Industry – A Case Study.” Journal 

of Environmental Science Engineering, 46 (2004): 49.

520 Olaosum, A., O. Ogundiran, and J. Tobih. “Health Hazards of Noise: A Review Article.” Research Journal of 

Medical Sciences, 3 (2009): 115. 521 National Academy of Sciences, Institute of Medicine, Board on Health Care Services. Keeping Patients Safe: 

Transforming the Work Environment for Nurses. National Academies Press, 2004.

522 International Organization for Standardization. Acoustics—Noise Emitted by Machinery and Equipment—

Determination of Emission Sound Pressure Levels at a Work Station and at Other Specified Positions in an 

Essentially Free Field over a Reflecting Plane with Negligible Environmental Corrections, ISO 11201:2010. 

International Organization for Standardization, 2010. 523 U.S. Department of Labor, Occupational Safety & Health Administration. Regulations (Standards—29 CFR), 

Part 1910.95: Occupational Noise Exposure. Occupational Safety & Health Administration, 1991.

524 Carayon, P., C. Alvarado, and A. Hundt. Reducing Workload and Increasing Patient Safety through Work and 

Workspace Design. Center for Quality and Productivity Improvement, University of Wisconsin-Madison, 2003.

525 Rosekind, M., P. Gander, L. Cornell, et al. Crew Factors in Flight Operations X: Alertness Management in 

Flight Operations Education Module. National Aeronautics and Space Administration, 2001.

526 Ibid.
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the time of the incidents.527 The use of private office space significantly reduces the occurrences 

of interruption due to conversation. While not the preferred arrangement, semi-private designs 

can offer some protection when arranged so that examiners do not directly face each other.

Examples of other forms of communication that can interrupt the cognitive process include 

phones, paging systems, and email. It is possible to control each of these in the office design. In 

this case, operational policies should address when it is permissible to mute such 

communications systems. The NIST team observed that although examiners were more likely to 

comment on the distracting effect of telephone and paging systems, greater attention was given 

to the Internet when it was available. 

The fact that an examiner has many responsibilities complicates the issue of interruptions. 

Serving in a training, supervisory, or management role, being called as a witness for the court, 

and being on-call to respond to crime scenes may sometimes affect an ongoing examination. 

Careful management can mitigate the effects through appropriate scheduling. In addition, 

examiners who also serve as crime scene technicians should be neither required nor permitted to 

monitor a dispatch radio for purposes of taking calls for service. Many individuals who become 

accustomed to being on call fail to recognize the cognitive effort required to be attentive to what 

is being broadcast. Managers should rely on alternative forms of notification, including a 

screening process by staff members outside the examination work area. 

Location

Location refers to the environmental and physical characteristics of the workspace. Of concern is 

how the physical environment influences system design and usage. The NIST team observed the 

impact of location on various aspects, including: 

• Too many disparate systems located on multiple workstations and platforms make it 

difficult to design the system to meet the user’s anthropometric and ergonomic 

requirements;

• Not all examiners work in a laboratory environment—some work in cubicles, others 

share office space, and some have private offices—which complicates a consistent 

ergonomic design; and

• Laboratories have increased levels of noise and movement due to multiple processes 

occurring over multiple workstations. 

Since latent print examination is not always limited to a side-by-side comparison capable of being 

performed in a single confined space, such as a desktop, examiners must interface with multiple 

systems during the workday. Examiners often use AFIS and digital imaging systems that are not 

well integrated and that reside on disparate workstations. As a result, routine task completion 

requires a great deal of movement between workstations, across multiple interfaces, and 

sometimes between rooms. This activity causes the examiner to move from one space to another 

carrying case files and evidence, which reduces efficiency and increases the potential for error. 

 

527 Dismukes, K., G. Young, and R. Sumwalt. Cockpit Interruptions and Distractions: Effective Management 

Requires A Careful Balancing Act. National Aeronautics and Space Administration, 1998.
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Office designs that situate all necessary equipment and workstations within a single area will 

mitigate these concerns. 

Managers, in consultation with human factors experts, should consider gathering information on 

the frequency and pattern of examiner movement and behaviors while completing tasks. This 

could assist in integrating systems through middleware to allow operation via a single interface or 

station wherever possible. If this is not possible, managers should consider the use of keyboard 

and monitor switches to allow access to multiple terminals from one workstation to reduce 

movement across offices. 

Stress

When individuals assess their circumstances as causing stress, their bodies automatically begin a 

series of stress-response mechanisms comprised of physiological, behavioral, and psychological 

efforts to adapt to the environmental demands.528 

Depending on the resources available within a particular agency, it is common for examiners to 

spend significant time in ancillary activities, such as maintaining equipment, managing office 

supplies, performing data entry tasks, preparing case file folders, inventorying and preparing 

case files for archived storage, and serving as phone operators. Such responsibilities can lead to 

inefficiency, decreased worker satisfaction, and frustration. 

During the NIST team observations, examiners frequently mentioned that they were responsible 

for managing information technology (IT) file backups, system or component selection and 

installation, integration, and troubleshooting. They also noted that IT support staff members 

scheduled routine systems maintenance at peak work periods. This activity led to reduced 

productivity, frustration, and potential errors due to the unexpected interruptions while casework 

was being performed. The impact of these interruptions led to one examiner’s decision to move 

to another laboratory. Managers should interview examiners to determine what workplace 

characteristics are considered distracting and stressful and should eliminate any unnecessary 

stressors from the work environment. 

7.4 Summary

Workspace design has a substantial impact on employees’ productivity, errors, and injuries. A 

usable latent print examination environment takes into consideration the needs of each examiner 

to develop an environment that improves productivity, reduces the complexity of the work, 

increases satisfaction, and reduces the risks of errors and injury.529

 

528 Cohen, S. and M. Rodriguez. “Pathways Linking Affective Disturbances and Physical Disorders.” Health 

Psychology, 14 (1995): 374.

Examiners’ office spaces must 

reflect good ergonomic design. The workspace and equipment must meet the individual 

examiner’s physical and cognitive needs. Systems should be integrated and standardized to 

reduce the amount of learning required to complete routine tasks over systems interfaces and 

office locations. The work environment cannot be designed with a one-size-fits-all approach. 

However, implementing the recommendations in this chapter, employing good ergonomic design 

529 Hendrick, H. “Determining the Cost-Benefits of Ergonomics Projects and Factors That Lead to Their Success.” 

Applied Ergonomics, 34 (2003): 419.
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principles, and adhering to usability guidelines and standards will improve the environment for 

the examiners. 
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Appendix 7-A: Design Processes

A.1 User-Centered Design Process

At its core, user-centered design is based upon the concept of developing usable, useful products. 

Each user and his context of use must define the user needs. Optimizing safety, comfort, 

efficiency, effectiveness, and user satisfaction requires an understanding and application of 

usability and the user-centered design process.

Table 7.2 lists usability goals and provides a short description of each, as adapted from Nielsen’s 

definition of usability quality metrics. It also provides some questions for latent print examiner 

environment designers to consider. When designing any usable system, it is important to consider 

these aspects of the user experience. 

Usability Goals Definition Latent Print Examiner-Targeted Questions

Effectiveness Measure of how well a user can 

perform a task

Can examiners successfully encode a print for 

submission to AFIS?

Can examiners accurately determine the 

orientation of the print? 

Efficiency Measure of how quickly a user 

can perform work and the 

accompanying error rate

Are examiners able to quickly accomplish 

goals?

Can examiners perform tasks with few errors?

Satisfaction Measure of user attitudes, 

perceptions, feelings, and opinions 

regarding the environment 

How well does the environment avoid 

inducing examiner discomfort and frustration? 

Are examiners intimidated by the 

environment?

Learnability Measure of how quickly a user 

can become productive

Can examiners learn how to use the tools and 

systems?

How long should it take an examiner to learn

the tools and system?

Are examiners able to use the tools and 

systems (to some defined level of 

competence) after instructions or training?

Memorability Measure of how well a returning 

user forms a mental model of the 

environment and remembers how 

to use it 

If an examiner has used the tool or process 

before, can he remember enough to use it 

effectively the next time, or does he have to 

re-learn it? 

How do experienced examiners differ from 

infrequent/novice examiners? 

After not using the tool or process for a period 

of time, how long should it take for the 

examiner to become familiar with it again?

Table 7.2: Definitions of usability goals and questions that apply specifically to latent print 

examiners530

 

530 Nielsen, op. cit.
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A.2 Iterative Process

Users who are included in the early stages of the design phase can provide feedback and 

recommendations that designers can incorporate into the initial prototypes. Designers of the most 

successful environments continually refine their prototypes through an iterative, evolutionary 

process with users. This iterative process must be user-centered, research-based, and 

performance-driven. 

User-Centered: 

• Identifies the types of users who will be using the workspaces, including latent print 

examiners, forensic specialists, and laboratory managers

• Ensures that the needs of the users are considered in the design and development of the 

environment 

Research-Based:

• Employs research to learn about users and their needs, tasks, environments, level of 

expertise, etc. 

• Conducts ongoing research with examiners by observing them interacting with the 

workspaces, systems, and hardware 

Performance-Driven: 

• Utilizes information gathered from users and measures user performance to ensure that 

design improvements have a measurable impact on users’ effectiveness, efficiency, and 

satisfaction 

A.3 Context of Use

During the first stage of the user-centered design process, the environmental designer must 

consider the “context of use.” The actual conditions under which latent print examination 

environments are used must be considered to ensure that the design of the environment will meet 

the needs of users and the objectives of the organization. 

Throughout the development process (and especially during the early stages of the design 

process), designers must be aware of contextual factors that include the business, operational, and 

social environments in which the system will be used.

A.4 Defining the Users

The central objective of designing a usable environment is to meet the needs of users within their 

operational context. The design of the environment should focus on users’ needs and 

expectations, involve users throughout, and integrate feedback from users into the design.

Recognizing the full range of users, designers should define the role each user will have within 

the examiner environment. Designers should try to understand the users’ needs, interests, and 

goals. Table 7.3 lists information about users that can be relevant to the design of the latent print 

examiner’s workspace. 
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Table 7.3: Characteristics to consider when designing latent print examiners’ work 

environments

A.5 Designing the User Environment

Once the characteristics have been defined, designers can begin to consider other environmental 

factors. For example:

• When and where will users analyze prints, compare prints, evaluate prints, and verify 

prints? 

• When and where will they interact with AFIS databases or other software systems?

• What are the characteristics of the environment, including physical infrastructure; 

configuration of workstation; placement of workstation; seating; height, angle, and 

distance from user; lighting; noise levels; frequency of tours; temperature and humidity; 

placement, type, and format of training materials, policies, procedures, and safety 

equipment; and the types of help that are available? 

Questions to Consider when Defining Users’ Requirements

Characteristics Characteristic Specifics User Requirements

Age What is the age range of this user group? Does age impact the use of 

technology (e.g., marking digital

images versus photographs)? 

Anthropometrics What are the heights of the users? 

What are the heights of the workstations?

Are the workstations’ heights 

adjustable?

Are the chairs’ heights adjustable?

Can the users reach the tools required 

for the tasks? 

Education What is the typical education level of the 

users?

How does education affect system 

usage? 

Experience and 

Knowledge Level

How much computer experience do the 

users have?

How many of the users have experience 

with AFIS databases?

How many of the users are new to the 

system?

How have users been trained on the 

system?

Do the needs of first-time users differ 

from those of more frequent users? 

Does the system need to 

accommodate users with training 

needs? 

Visual Attributes Do any of the users have color blindness?

Do any of the users have contrast 

sensitivity?

Do any of the users have dyslexia?

Do users have other characteristics with 

respect to visual acuity or other factors?

How do these attributes affect the 

environmental design? 
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Designers can use Table 7.4 to help them identify how the environment will be used, to define 

possible user requirements and to ask design questions relating to each element of the workspace 

and environment. 

Questions to Consider

Characteristics Characteristic Specifics Potential Effects

Location In what environment will the 

workstation be located?

What are the physical characteristics 

of this location? 

Within the location, how will the 

workstation be situated?

How does the physical 

environment of this location 

affect or influence the design and 

usage of the system? 

How does the placement of the 

workstation affect use of and 

access to the system?

What spatial requirements are 

necessary to facilitate frequent 

use?

Temperature and Humidity What is the average temperature for 

the location? 

What are the extreme temperatures? 

Is the area humid? 

How do temperature and 

humidity affect the users? 

How does the outside 

environment affect performance? 

Lighting What types of lighting are utilized?

Will the system be utilized at night as 

well as during the day?

How does the level of lighting 

affect readability and visibility? 

Noise What is the average noise level? How does the noise level affect 

an individual’s ability to 

perform?

Instructions/Warnings Where are instructions placed?

What is the format of instructions 

(e.g., signs, labels, icons)? 

Are the instructions large 

enough? 

Are the instructions obstructed?

What is the appropriate height to 

place instructional guides?

Assistance What types of help and assistance are 

provided? 

Given the environment, what is 

the best way to present error 

feedback and helpful 

information?

Table 7.4: Characteristics regarding each element of an environment
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A.6 Defining User Goals and Tasks

After identifying user characteristics and task requirements, designers should conduct a user and 

task analysis by answering questions such as: 

• What is the user’s purpose? 

• What are the user’s needs, interests, and goals?

• How will the user interact with the environment?

• What are the key tasks the user must perform?

• Which tasks will the user perform frequently? 

• Which tasks are critical to the user’s success in the environment?

• Which tasks are critical to the success of the organization? 

Designers should consider how human factors issues affect each task. Important tasks that could 

be affected by human factors issues should be evaluated first. Designers should consider these 

questions for each group of users identified in the previous section. 
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Chapter 8: Training and Education 

163 

Chapter 8: Training and Education

Introduction and Scope

This chapter reviews the history and current state of latent print examiner training programs, 

standards, and requirements. It identifies shortcomings in the current system and offers 

recommendations to improve training through research into and development of effective 

mentoring programs and comprehensive training materials. The chapter also discusses existing 

standards of professional organizations, requirements for accreditation, and benefits of 

certification. It recommends mandatory certification and accreditation to improve the latent print 

field as a whole. 

8.1 A History of Training in the United States

The first formal training for latent print examiners in the United States took place during the 

1904 World’s Fair in St. Louis when Sergeant John K. Ferrier of Scotland Yard’s Fingerprint 

Bureau provided brief “instructions to hundreds of police officers and prison officials.”531 He 

then conducted a 7-month training session for 9 people on the comparison of unknown 

fingerprint specimens to known exemplars and the classification of fingerprint records.532 

By 1915, the International Association for Criminal Identification (later, the International 

Association for Identification, or IAI) was formed. One objective was “to provide training, 

education, and the publication of information in all forensic disciplines represented by this

Association.”533 The Association also instituted an annual training seminar.534

In 1916, T. G. Cooke and W. K. Evans created a school in Chicago to offer a home-study course. 

The school had several names until, in 1926, it became the Institute of Applied Science (IAS). 

The IAS course proceeded through various functional areas with reading and competency 

testing. Graduation usually required a year and a half of “study monitored and directed by 

personal and highly professional, albeit long distance, tutelage. ... By 1937, and continuing for 

many years after, nearly one half of the individuals in charge of fingerprint bureaus in North 

America were IAS graduates.”535

In 1924, the Federal Bureau of Investigation (FBI) created an Identification Division. It offered a

2-week fingerprint examiner training program for law enforcement agencies throughout the 

country.536

 

531 Grieve, D. “The Identification Process: Traditions in Training.” Journal of Forensic Identification, 40 (1990): 

199.

The first week of the program dealt with recognizing fingerprint types, identifying 

characteristics, and classifying fingerprint records. The second week focused on comparing 

532 Ibid., p. 209. 533 International Association for Identification. Constitution, Article 1, Section 1.03f. International Association for 

Identification, 2011.

534 Grieve, op. cit., p. 206. 535 Ibid., p. 207. 536 Federal Bureau of Investigation. The Science of Fingerprints: Classification and Uses. U.S. Department of 

Justice, 1979.
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unknown fingerprint specimens to known fingerprint records. The program concentrated on the 

development of the skills needed for comparing fingerprints and for developing latent prints. It 

did not concern itself with the underlying science that made the work plausible or with 

instruction in scientific methodology. 

“Ridgeology,”537 a holistic approach to the latent print comparison process that goes beyond the 

counting and arrangement of friction ridge minutiae, required latent print examiners to learn 

more about friction ridge skin, its discriminating features, and the comparison process. Some 

larger agencies created their own training programs, but most small providers relied on existing 

examiners to train new ones informally. Without the leadership of a central authority, no formal 

training program emerged. 

The IAI and the Scientific Working Group for Friction Ridge Analysis, Study and Technology 

(SWGFAST) have published suggestions concerning training programs for latent print 

examiners.538 Although these documents outline the training needs for examiners, neither 

organization provides training materials (see section 8.4).

Today, forensic examiners receive training through a wide variety of programs and approaches, 

and they follow a range of educational pathways that lead to careers in latent print 

examination.539 Latent print examiners may receive some training as part of a formal 

undergraduate or graduate program in forensic science or criminal justice, or they may have 

acquired their professional skills through on-the-job training.540 Latent print examiners usually 

work at law enforcement agencies where training comes from internal mentorships, sometimes 

supplemented by external programs and formal training. In this traditional approach, one 

generation of trainers transmits its knowledge and skill to the next.541 

8.2 Concerns about the Current Training System

Today’s variegated system of training has some benefits, but it lacks uniformity and raises 

concerns about quality. For example, the 2009 National Research Council report on forensic 

science in the United States observes that latent print training varies from agency to agency and 

may include “a formalized training program, may use an informal mentoring process, or may 

 

537 Ashbaugh, D. Ridgeology: Modern Evaluative Friction Ridge Identification. Royal Canadian Mounted Police, 

1999.

538 International Association for Identification. Friction Ridge Skin Identification Training Manual. International 

Association for Identification, 2006; Scientific Working Group on Friction Ridge Analysis, Study and Technology. 

Standards for the Minimum Qualifications and Training to Competency for Friction Ridge Examiner Trainees 

(Latent/Tenprint). Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, 

February 2010.

539 Gaensslen, R. “How Do I Become a Forensic Scientist?, Educational Pathways to Forensic Science Careers.” 

Analytical and Bioanalytical Chemistry, 376 (2003): 1151–55.

540 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Strengthening Forensic Science in 

the United States: A Path Forward, Position Statement. Scientific Working Group on Friction Ridge Analysis, 

Study and Technology, 2009.

541 In 1990, David Grieve wrote that “fingerprint training is centered around some type of apprenticeship that 

contains varying amounts of tutelage, on-the-job training, or self study. Structured, formal courses that provide 

complete instruction, either academic or employer designed, are rare.” Grieve, op. cit., p. 195.
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165 

send new examiners to a 1- to 2-week course.”542 This lack of standardized training can lead to a 

wide range of practices. Informal training programs vary in length from weeks to years, and 

testing for competency may not exist within each department.

Recent years have brought notable efforts to standardize formal academic programs in forensic 

science;543 however, much of the analysis of education and training has focused on forensic 

science degree-granting programs, neglecting training specific to latent print examination. The 

absence of enforceable standards has led to heterogeneity in curricula, instructors, pedagogy, 

documentation, and mentorships. Some agencies do not have staff members available to mentor 

trainees adequately, and even when mentors are available, it is not clear how they are selected or 

trained.

Smaller agencies with only a handful of examiners often find it particularly challenging to 

provide adequate training. Training might be limited to the most practical aspects of the job, as 

pressures are in place to apprentice and to manage the caseload. Because of the lack of 

industry-wide standards, training is limited to the level of expertise of the trainer, which can lead 

to perpetuation of improper or inappropriate methods. Limited career paths in smaller agencies 

can create high turnover rates that make it constantly necessary to train new examiners. 

A few professional and private organizations supply advanced training and education. However, 

there has been little to no effort to evaluate the content of the training to show its 

effectiveness.544 Furthermore, only a fraction of all examiners participate in these courses, 

leaving the field without uniform standards and requirements for education and training, 

consistently qualified instructors, and comprehensive and updated curricula. 

8.3 Recommendations for Training

To improve the training system, it is necessary first to understand what skills and knowledge are 

necessary for latent print examination. Examiners must have the proper cognitive abilities to 

conduct latent print examinations and to communicate their findings. Specific abilities in 

perception and judgment are required for the analysis, comparison, and evaluation of friction 

ridge impressions. These go beyond screening for form blindness, color blindness, and visual 

acuity. 

 

542 National Academy of Sciences, National Research Council, Committee on Identifying the Needs of the Forensic 

Science Community. Strengthening Forensic Science in the United States: A Path Forward. National Academies 

Press, 2009, p. 136. For more extensive discussions, see Cowger, J. “Moving Towards Professionalization of Latent 

Print Examiners.” Journal of Forensic Sciences, 24 (1979): 591–95; Cooney, L. “Latent Print Training to 

Competency: Is it Time for a Universal Training Program?” Journal of Forensic Identification, 60 (2010): 223–58.

543 Technical Working Group for Education and Training in Forensic Science. Education and Training in Forensic 

Science: A Guide for Forensic Science Laboratories, Educational Institutions, and Students. National Institute of 

Justice, 2004; American Academy of Forensic Sciences, Forensic Science Education Programs Accreditation 

Commission. Accreditation Standards. American Academy of Forensic Sciences, revised July 22, 2011, Article I. 544 For additional information on ways to evaluate, see Kirkpatrick, D. and J. Kirkpatrick. Evaluating Training 

Programs: The Four Levels. 3rd ed. Berrett-Koehler Publishers, 2006.
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Recommendation 8.1: The federal government should consider funding research to 

determine what educational and cognitive abilities should be prerequisites for training 

a latent print examiner. Forensic service providers should have systematic training 

programs that develop these abilities as well as educate examiners in the scientific 

method, the relevant scientific literature, communication skills, and methods for 

logically developing conclusions. 

Once a systematic training program on all aspects of latent print examination is developed, it 

must be affordable to forensic service providers. Budgetary constraints limit the number of 

trainees who can be hired, and training through formal programs outside the agency can be 

costly. Previous federally funded incentive programs, such as the Law Enforcement Education 

Program (LEEP) and its successor, the U.S. Department of Justice Police Corps program, were 

designed to address similar concerns from a broader law enforcement perspective. The Police 

Corps program provided scholarships or tuition reimbursements in return for a 4-year 

commitment to work as patrol officers in a state or local law enforcement agency. Federal funds 

went to states to develop and provide training. In addition, the federal government provided local 

and state agencies that hired Police Corps officers $10,000 a year for 4 years of service. Similar 

incentives to support training, education, and salaries of latent print examiner trainees would 

encourage agencies to create positions or fill vacancies. 

Recommendation 8.2: The federal government should develop a forensic latent print 

examiner scholarship program to:

a. Fund the post-hire training program and, upon successful completion, provide 

tuition reimbursement, loan forgiveness, or other financial assistance to degreed 

latent print examiner trainees working in state, local, or private (not-for-profit) 

forensic laboratories; and

b. Reimburse the employer for a percentage of the salaries during the training 

period.

By learning what specific skills and knowledge are essential to successful latent print 

examinations and by implementing programs that allow all examiners to receive proper training, 

forensic service providers can ensure that their examiners have the tools they need and can pass 

this information on to newer employees. 

On-the-job relationships play a critical role in the professional development of new examiners. 

Such relationships provide opportunities to receive feedback, counseling, coaching, skill 

building, advancement, role modeling, and reinforcement.545 Informal relationships often occur 

naturally between co-workers. However, formal mentoring programs allow agencies to foster 

developmental relationships between junior and senior staff members by taking an active role in 

their initiation by assigning mentors and monitoring this relationship’s effectiveness. 

Organizational benefits of establishing formal mentoring programs include transferring 

organizational culture and institutional knowledge, reinforcing and encouraging teamwork, 

reducing stress, and decreasing turnover.546

 

545 Kram, K. and M. Bragar. “Career Development Through Mentoring: A Strategic Approach for the 1990s − Part 

I.” Mentoring International, 5, no. 3 (Summer 1991): 3–13.

 Research shows that successful mentoring programs 

546 Jorgenson, J. Mentoring Programs: An Overview. National Academy of Public Administration, 1992.
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include voluntary participation, matching mentors and protégés who are two to three levels apart, 

careful selection of mentors, flexible duration, one-on-one mentoring, a no-fault exit provision, a 

high priority on program evaluation, and the clear communication of mentoring objectives.547

Poor coordination of mentorship programs can lead to conflicts between the mentoring and 

supervisory roles of the mentor, breaches of confidentiality, mentor bias, lack of active listening, 

and role confusion.548 Agencies must take care to minimize these risks. 

Recommendation 8.3: Agencies should establish formal mentoring programs that define 

the roles and responsibilities of the mentor, trainee, and supervisor. 

The Working Group appreciates that agencies with limited staff may find it difficult to provide 

their own mentoring programs, but these agencies may develop cooperative agreements with 

neighboring jurisdictions to support the program. As in all educational programs, the mentors 

should be highly qualified. Mentors and instructors, whether in the workplace or in formal 

training and educational programs, should possess expert subject-matter knowledge that they can 

convey clearly and effectively. 

8.4 Recommendations for Curriculum and Information Resources

Although various training materials549 and texts550 for latent print examiners are published and 

available, there is a lack of centralized, easily accessible, and readily understandable sources of 

valid information. This gap leads to a related recommendation. 

Recommendation 8.4: The federal government should establish an expert group to 

develop a latent print educational textbook, practical exercises, and assessment tests 

(print and online) in consultation with professional organizations, senior latent print 

examiners, researchers with content knowledge, experienced trainers, and professionals 

experienced in curriculum development. 

In developing new curricula, trainers should consider the expertise of the targeted audience and 

the teaching and testing methods used.551

 

547 Ibid.; Wilson, J. and N. Elman. “Organizational Benefits of Mentoring.” The Executive, 4, no. 4 (1990): 88-94.

Content should be based upon published standards, 

peer-reviewed articles, and reference works. Terminology should be consistent throughout the 

materials. The content should extend beyond the biology and analysis of friction ridge skin. 

Authors should not be confined to experts in latent print examination, but should include experts 

548 Taherian, K. and M. Shekarchian. “Mentoring for Doctors: Do Its Benefits Outweigh Its Disadvantages?” 

Medical Teacher, 30 (2008): e95–e99.

549 See, e.g., IAI, op. cit. 550 See, e.g., Saferstein, R. Criminalistics: An Introduction to Forensic Science. Prentice Hall, 2000; Ashbaugh, D. 

Quantitative - Qualitative Friction Ridge Analysis: An Introduction to Basic and Advanced Ridgeology. CRC Press, 

1999; Vanderkolk, J. Forensic Comparative Science: Qualitative Quantitative Source Determination of Unique 

Impressions, Images, and Objects. Academic Press, 2009; Cowger, J. Friction Ridge Skin: Comparison and 

Identification of Fingerprints. CRC Press, 1992; Lee, H. and R. Gaensslen, ed. Advances in Fingerprint Technology. 

2nd ed. CRC Press, 2001; National Institute of Justice and Scientific Working Group on Friction Ridge Analysis, 

Study and Technology. The Fingerprint Sourcebook. National Institute of Justice, August 2011.

551 See, e.g., Tyler, R. Basic Principles of Curriculum and Instruction. University of Chicago Press, 1949. Tyler 

recommends defining appropriate learning objectives, introducing useful learning experiences, organizing 

experiences to maximize their effect, and evaluating the process and revising the areas that were not effective.
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168 

on cognitive issues, statistics, and forensic science. Hands-on exercises relating to bias and 

cognitive processing should be included. Ideally, the effectiveness of the materials should be 

evaluated before and after they are deployed. 

Recommendation 8.5: Training materials should include topics beyond the technical 

aspects of friction ridge analysis, such as: 

a. Documentation of work and case notes and written and oral communication; 

b. Professional ethics; 

c. Human factors issues such as fatigue, bias, cognitive influences, perceptual 

influences, and error; 

d. Research methods; and

e. Legal aspects of expert testimony.

Existing clearinghouses are an important resource for those undertaking educational and training 

activities. For example, the National Clearinghouse for Science, Technology and the Law 

(NCSTL) assembles into a publicly searchable database relevant scientific, technological, and 

legal resources and a bibliography specific to forensic science content areas, such as the 

reliability of automated fingerprint identification systems (AFIS).

552 Indeed, a resource 

comparable to the National Library of Medicine’s PubMed for forensic science could provide 

further benefits to researchers, especially given the limited accessibility of some forensic science 

publications.553 

Recommendation 8.6: The federal government should support a clearinghouse of 

materials from existing training programs as well as publications on latent print 

identification.

8.5 Existing Standards and Accreditation Requirements

Whatever training programs and materials are developed to supplement the current system, 

developing national standards and accreditation requirements are essential to demonstrating the 

effectiveness of training. Currently, professional organizations offer a mix of standards, 

recommendations, and requirements, but there is no single, national accreditation that indicates 

quality. 

8.5.1 Standards

Mandatory national standards for educational requirements and for a training curriculum for the 

forensic discipline of latent print examination do not exist, although the IAI and SWGFAST

outline the minimum requirements of a training program. 

In 1977, the IAI developed its Latent Print Certification Program, which includes education, 

training, and experience requirements leading to written and practical examinations. The IAI 

 

552 For one example of an NCSTL bibliography, see http://www.ncstl.org/education/AFISReliability (accessed 

November 29, 2011). Presumably, NCSTL tries to include all significant publications. Abstracts or annotations for 

these materials would enhance the value of the bibliography. 

553 See Mnookin, J., S. Cole, I. Dror, et al. “The Need for a Research Culture in the Forensic Sciences.” UCLA Law 

Review, 58 (2011): 725.
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requires a bachelor’s degree or years of experience as a prerequisite to certification in latent print 

examination. Various training courses are offered to help examiners prepare for the exam, but 

only one provider is affiliated with the IAI. Each IAI local division sponsors its own conferences 

and training. 

In addition, SWGFAST documents provide guidance for training programs, examiner 

qualifications, proficiency testing, and standardized practices and terminology.554 SWGFAST 

has established recommendations for training program content and participation competency. 

SWGFAST has also issued standards for friction ridge automation training that focus on image 

capturing and the history, theory, and operation of AFIS.555 

There have been calls for new examiners to have a science background. SWGFAST also 

recommends that latent print examiners possess a bachelor’s degree with some “science-related 

coursework.”556 It has been argued that forensic service providers must spend more time and 

resources to train applicants who lack this background.557 

8.5.2 Requirements for Accreditation

The American Society of Crime Laboratory Directors/Laboratory Accreditation Board 

(ASCLD/LAB), Forensic Quality Services, the American Association for Laboratory 

Accreditation, and other private organizations accredit forensic service providers. In response to 

a 2004 report from the National Institute of Justice,558 the American Academy of Forensic 

Sciences created a standing committee known as the Forensic Science Education Programs 

Accreditation Commission (FEPAC).

559 This Commission “accredits forensic science education 

programs that lead to a bachelor’s or master’s degree in forensic science or in natural science 

with a forensic science concentration.”560 The degree programs must be “located in a regionally 

accredited institution of higher education.”561 

ASCLD/LAB requires agencies to have a documented training program and to follow it; 

however, there is no guidance as to what the training curriculum should encompass. In a 2009 

survey, 75% of the agencies responding reported a formal written training program in 

compliance with accreditation requirements.562

 

554 Ibid.

 The survey found no significant differences 

between accredited and non-accredited agencies with regard to aspects of training, such as the 

number of comparisons needed, the period of supervised case review, pass-fail policies, and the 

existence of a dedicated trainer. However, the low response rate for the survey and the possible 

lack of statistical power make these results difficult to interpret.

555 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standard for Friction Ridge 

Automation Training (Latent/Tenprint). Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study 

and Technology, May 2009.

556 SWGFAST, 2010, op. cit. 557 Stoney, D. “A Medical Model for Criminalistics Education.” Journal of Forensic Sciences, 33 (1988): 1086–94.

558 Technical Working Group for Education and Training in Forensic Science, op. cit. 559 American Academy of Forensic Sciences, Forensic Science Education Programs Accreditation Commission, op. 

cit., section 1.3.

560 Ibid., section 1.4.

561 Ibid.

562 Cooney, op. cit. 
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8.6 Recommendations for Certification and Continuing Education

Professional certification and accreditation programs typically require some form of continuing 

education. Continuing education opportunities in the forensic sciences include courses, 

professional conferences and seminars, distance learning, apprenticeships, residency, internships, 

teaching, and independent learning.563 Latent print examiners should be encouraged to pursue 

opportunities for such continuing professional education. 

Ongoing education that enhances and improves current latent print work activities could include 

an introduction to cognitive processes, statistical data on fingerprint features, basic probability 

theory, technological developments, and the ethical and legal responsibilities of latent print 

examiners. Management should be aware of the skills and expertise of examiners in order to 

identify gaps that could be eliminated through continuing education and training. 

Two major impediments to continuing education programs are cost and access. If programs are 

not located nearby, or if the costs of enrollment are too high, some examiners will be precluded 

from continuing education opportunities. To address this issue, the National Institute of Justice 

provides funding for the development and delivery of online continuing education for forensic 

scientists and professionals at various levels of knowledge and practice.564 

Recommendation 8.7: Forensic service providers should require personnel to 

participate in continuing education and to become certified through an accredited 

program. Certifying bodies should review current certification tests with the aid of 

professionals in test design and psychometrics.

Some jurisdictions have moved toward requiring certification of examiners and accreditation of 

laboratories.565 By earning certification, examiners demonstrate their professional competence 

and set a knowledge and experience base for themselves, for their employers, and for the public 

at large. Additionally, certification has benefits beyond those provided to the individual 

examiner. 

• Team performance increases each time a new team member is certified; 

• The level of skill that a team has directly affects its performance;

• Certification standardizes practices within the industry and leads to more cooperation 

among organizations; 

• Individuals who earn certification have shown their dedication to personal 

accomplishment and improvement and may increase their career opportunities; and 

 

563 Technical Working Group for Education and Training in Forensic Science, op. cit. 564 U.S. Department of Justice, National Institute of Justice. “Training.” Accessed November 29, 2011. 

http://www.nij.gov/training/welcome.htm; RTI International. “Forensic Science Education: Web-Based Professional 

Development and Continuing Education for Forensic Scientists.” Accessed November 29, 2011. 

http://www.rti.org/page.cfm/Forensic_Science_Education.

565 New York, Oklahoma, and Texas have state accreditation requirements. National Conference of State 

Legislatures. Strengthening Forensic Science Oversight. National Conference of State Legislatures, February 2010.
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Chapter 8: Training and Education 

171 

• The public has more confidence in individuals who are certified as meeting some quality 

standard.566 

By requiring certification of examiners, forensic service providers can ensure and demonstrate 

that their employees are competent, knowledgeable, and skilled at all aspects of the latent print 

examination process. 

8.7 Evaluation of Training Programs

Although FEPAC evaluates and accredits forensic science curriculum in degree-granting 

academic institutions, other forensic science training programs do not receive review or 

evaluation. Laboratory accreditation and examiner certification programs include educational 

and training requirements. However, these requirements only verify that education and training 

have occurred; they do not assess the quality of the training programs.567 

Certifying and accrediting bodies should evaluate training material and training programs. 

Evaluation methods could include student surveys, measurements against defined learning 

objectives, or documentation of outcomes. Professional organizations offering training should 

actively seek a means for external evaluation of their programs. 

Recommendation 8.8: Certifying bodies should ensure that examiners have been 

trained to competency. Laboratory accrediting bodies should evaluate the effectiveness 

of an agency’s training program. 

8.8 Summary

Although some training programs and informational resources exist to educate latent print 

examiners, improvement will require a shift to a single, national standard training system that 

covers more than the technical tasks involved in latent print examination. A comprehensive 

training program should include information about report writing, testifying, maintaining 

professional and personal ethics, understanding the influence of cognitive bias, and calculating 

statistics. Certification and accreditation organizations should review the effectiveness of new 

training programs, and forensic science providers should require their examiners to earn 

certification to demonstrate their commitment to quality. 

 

566 Microsoft Learning Whitepaper. The Value of Certification: Connecting the Dots Between Employers and 

Employees. Microsoft Corporation, March 2007; SeaCrest Company. “The Value of Certification.” Credentialing 

Talk, August 1, 2007. Accessed October 21, 2011. http://seacrestcompany.blogspot.com/2007/08/value-ofaccreditation.html.

567 For additional discussion of certification, see Chapter 9.
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Chapter 9: Human Factors Issues for Management

Introduction

The primary responsibility of management is to develop policies and to promote a culture for

successful completion of tasks. Other chapters in this report focus on factors that affect the 

quality of the work in a latent print unit. These include the work environment (Chapter 7), skills 

and expertise in interpreting prints (Chapter 3), technology (Chapter 4), reporting and testimony 

(Chapters 5 and 6), and personnel training (Chapter 8). Management plays a central role in all 

those areas by establishing strategies and a culture that recognizes and responds to human factors 

in latent print examination. 

Managers must be committed to developing, maintaining, and improving quality assurance (QA) 

and quality control (QC) processes. QA includes procedures to ensure that final results are valid, 

and QC includes monitoring to verify that procedures are working.568 Taken together, QA and 

QC constitute a quality management system. This chapter focuses on the responsibilities of 

management in creating an environment that enhances quality through certification, 

accreditation, and proficiency testing as well as a systems approach to reducing errors. 

9.1 A Management Perspective on Errors

Chapter 2 describes the types of errors that can occur in the complex endeavor of latent print 

examination. That chapter used four categories for the possible outcomes of a latent print 

examination—identification, inconclusive, exclusion, and not suitable for comparison 

(insufficient data). However, forensic service providers differ in the number and names of 

possible outcomes of latent print examinations. This chapter uses a more elaborate typology with 

five categories: identification, inclusion, inconclusive, exclusion, and not suitable. 

In casework, examiners do not start with knowledge of the truth. They reach conclusions based 

upon knowledge, training, and experience. The quality management system should continually 

evaluate performance. Part of this system is the review of the examiner’s results by another 

qualified examiner. If there is conflict, the agency must employ a pre-determined procedure for 

resolving the conflict. Having determined the result judged to be “correct,” the agency would 

attribute an “error” to one of the examiners. For example, the two images in Figure 9.1 would 

produce a very complex comparison that could generate different results from different 

examiners.

 

568 Deming, W. Out of the Crisis. Massachusetts Institute of Technology, Center for Advanced Educational Services, 

1986.
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Figure 9.1: Latent print from an ashtray and an exemplar print569

Presented with this pair of prints, five different examiners might each report a different 

conclusion, as shown in Table 9.1. 

Examiner Result Explanation 

1 Identification The examiner determined that there is enough similarity between the latent 

and exemplar to make an identification.

2 Inclusion The examiner found detail in agreement; however, due to the limited

quality of the latent print, a conclusive identification was not possible. The 

examiner also determined that selection of additional print details would 

not result in a more definitive conclusion. 

3 Inconclusive The examiner could not determine if there was sufficient agreement 

between the latent print and the exemplar print but believes that additional 

exemplars could aid in the assessment. 

4 Exclusion The examiner found similarities between the latent print and the exemplar 

print but interpreted the distortion artifacts in the latent print as actual 

friction ridge detail and determined that these two impressions came from 

different sources.

5 Not Suitable The examiner determined the latent print was not suitable for comparison 

and therefore never compared the latent print to any exemplars.

Table 9.1: Five possible outcomes of the comparison of the latent and exemplar prints in Figure 9.1 

If the two prints come from the same source, the conclusions of examiners 3, 4, and 5 may 

preclude the conviction of a criminal. If the impressions did not originate from the same source, 

then the conclusions reported by examiners 1 and 2 may contribute to the arrest and prosecution 

of an innocent person. Procedures that permit an agency to determine which results are most 

 

569 Image adapted courtesy of the Las Vegas Metropolitan Police Department. 

Latent print Exemplar print
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Chapter 9: Human Factors Issues for Management

174 

likely to be correct, to detect departures from those results, and to investigate the factors that led 

to the deviations are critical to the quality management process.

Table 9.2 enumerates the various possible erroneous outcomes in the above example. “Error” in 

the table is defined relative to the outcome judged to be most acceptable rather than relative to 

the unknown states of nature (see Chapters 2 and 3). 

Result Judged To Be Correct

Identification Inclusion Inconclusive Exclusion Not Suitable

Examiner’s Result

Identification CORRECT Erroneous 

Identification

Erroneous 

Identification

Erroneous 

Identification

Erroneous 

Identification

Inclusion Failure to 

Identify 

CORRECT Erroneous 

Inclusion 

Erroneous 

Inclusion 

Erroneous 

Inclusion 

Inconclusive Failure to 

Identify 

Failure to 

Include 

CORRECT Failure to 

Exclude 

Erroneous 

Suitability 

Determination

Exclusion Erroneous 

Exclusion 

Erroneous 

Exclusion 

Erroneous 

Exclusion 

CORRECT Erroneous 

Exclusion 

Not Suitable Failure to 

Identify 

Failure to 

Include 

Erroneous 

Suitability 

Determination

Failure to 

Exclude 

CORRECT

Table 9.2: Concordance table listing possible “errors” for conclusions in Table 9.1

The agency’s quality management system should track the errors listed above. When errors 

(either in the sense defined above or relative to ground truth) are detected, it is critical to 

understand the factors (see appendices) that led to them. By strengthening the quality 

management system to guard against those factors, the risk of errors can be reduced. 

9.2 A Systems Approach to Improving Accuracy

From the systems perspective outlined in Chapter 2, human error in the workplace is not an 

isolated action of a given individual. Rather, it is the result of a chain of events that cumulate in 

the adverse event. Since Heinrich’s 1931 publication, industry has embraced a sequential theory 

of human error.570 James Reason’s 1990 “Swiss cheese” model examines error systematically. It 

assumes that there are fundamental elements of all organizations that must work together 

harmoniously to achieve efficient and safe operations.571 Taken together, these elements 

comprise a “productive system” as depicted in Figure 9.2, an adaptation of Reason’s model. 

 

570 Heinrich, H., D. Peterson, and N. Roos. Industrial Accident Prevention: A Safety Management Approach. 1st ed. 

1931.

571 Reason, J. Human Error. Cambridge University Press, 1990.
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Figure 9.2: Components of a productive system adapted to a latent print unit572

For our purposes, the four slices from Reason’s original model have been renamed as Examiner 

Actions, Conditions that Affect Performance, Supervisory Issues, and Organizational Influences. 

Examiner actions are the mistakes or violations by the examiner. They are what the examiner 

did. Conditions that affect performance are factors related to the condition of the examiner, 

communication, or the environment that influenced the examiner. Supervisory issues are any 

failures in the supervision of the examiner. Lastly, organizational influences are management 

decisions and the organizational climate that affect the examiner. All require analysis and 

discussion, and Appendix A lists examples of actions in each category. 

Based upon this model, forensic analysis can be viewed as a complex system whose product is 

the interpretation of forensic evidence. Productive activities within a latent print unit require 

reliable, well-maintained equipment and a well-trained professional workforce. These are 

included in the Conditions that Affect Performance slice in Figure 9.2. Examiners also need good 

management and effective supervision, and managers need appropriate guidance, personnel, and 

funding to perform their duties, which is represented in the Supervisory Issues slice. The support 

of management comes from decision-makers who set goals and manage available resources, 

represented by the Organizational Influences slice. They must balance oft-competing goals of 

throughput, due diligence, and resources. These executive decisions typically are based upon 

social, economic, and political input from outside the organization as well as on feedback from 

managers and workers within it. 

Accidents occur when there are breakdowns in the interaction among the components in the 

production process.573

 

572 Image adapted from Reason, op. cit.

These failures, shown as holes in the different slices, make the system 

more vulnerable to error, especially when there are multiple failures at each level. Using the 

573 Ibid.
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“Swiss cheese” model of error causation, an error occurs when the holes from each slice are 

aligned. 

There are two necessary ingredients to identifying weaknesses in a forensic system: (1) a human 

error model to capture and organize the information and (2) forensic experts to analyze the 

examination process and to identify the human and other factors that can affect the outcome. The 

literature contains many human error models.574 If the underlying assumptions regarding the 

nature and cause of error are considered, there are six different perspectives to error 

investigation: cognitive, ergonomic, behavioral, medical, psychosocial, and organizational.575

Each perspective on human error investigation has its advantages. Many industries therefore 

have employed a multi-perspective approach, using models such as root cause analysis, failure 

mode and effects analysis, a management oversight risk tree, a safety management organization 

review technique, and the human factors and analysis classifications system (HFACS). This 

chapter uses HFACS as a framework for discussion,

576 but other error models would elucidate 

the same factors. 

9.2.1 Examiner Actions

Problematic actions of the examiner can be loosely classified as either mistakes or violations. 

Mistakes represent normal behavior that fails to produce the desired outcome. Violations refer to 

the willful disregard of accepted practices. These mistakes and violations should be considered in 

more detail. 

Decision-, Skill-, and Perception-Based Mistakes

Decisions are based primarily on three factors: information, knowledge, and experience (see 

Chapter 3). In latent print examination, information lies in the latent and exemplar prints, which 

must be of sufficient quality and quantity to compare and evaluate. In addition, the examiner 

should be provided with other information, such as the surface from which the latent prints were 

recovered, the technique used to develop and recover the latent prints, and the method used to 

capture the exemplar prints. The examiner applies training, background knowledge, and 

experience comparing a broad range of pairs of latent and exemplar prints to assess the available 

information. When important information, knowledge, or experience is lacking, mistakes can 

occur. Often referred to as honest mistakes, these mistakes typically present themselves as poorly 

executed procedures, improper choices, or the misinterpretation or misuse of relevant 

information. 

Other mistakes occur with little or no conscious thought. For instance, during latent print 

examination, examiners can orient many latent prints without conscious attention. Tasks such as 

these highly practiced and automatic behaviors are particularly affected by attention or memory 

failures. Distractions in the laboratory (see Chapter 7) may lead to a loss of concentration, 

erroneous documentation, and other mistakes. 

 

574 Senders, J. and N. Moray. Human Error: Cause, Prediction, and Reduction. Psychology Press, 1991. 575 Wiegmann, D. and S. Shappell. A Human Error Approach to Aviation Accident Analysis: The Human Factors 

Analysis and Classification System. Ashgate Publishing, 2003.

576 Ibid.
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Additionally, mistakes can 

occur as a result of the manner 

in which the examiners store 

and compare latent print data. 

For instance, when latent and 

exemplar prints have only 

limited corresponding 

information, the examiner must 

search different regions of the 

latent print separately, breaking 

up the pattern of data and 

searching each component. 

Examiners who are inclined to 

search the latent print as a 

complete image (searching for 

the whole pattern) can fail to 

identify the latent print or can 

erroneously exclude the 

exemplar.

Examples of these types of 

mistakes in latent print 

examination are failures to find 

target data, to properly weight 

the data, to recognize distortion, 

and to compare enough 

corresponding features. These 

types of mistakes can lead to a 

conclusion exceeding the ability 

of the examiner, a failure to 

search all exemplars, a hurried 

or insufficiently thorough 

examination, insufficient data to 

support the conclusion, a 

mis-prioritized level of effort, 

and improperly deeming a print 

to be suitable or unsuitable. 

 

577 Camp, R. Business Process Benchmarking: Finding and Implementing Best Practices. ASQC Quality Press, 

1995. 

578 American College of Emergency Physicians. Benchmarking in Emergency Medicine, March 1997. Accessed 

November 29, 2011. http://www.acep.org/content.aspx?id=34362.

579 Ibid.

580 Emergency Department Benchmarking Alliance. About Us. Accessed November 29, 2011. 

http://edbenchmarking.org/index.php. 581 Augustine, J. “ED Wait Times Improving for the First Time in 40 Years.” Improving Health Care, Press Ganey. 

February 21, 2011.

Box 9.1: Learning from Others: Benchmarking in 

Forensic Science

Forensic laboratories and latent print examiners can learn from 

each other and from other industries to improve procedures and 

human factors considerations. This process, called benchmarking, 

is primarily associated with actions that Xerox took in the early 

1980s to remain competitive with companies that were producing 

less expensive and higher quality copiers. Xerox not only studied 

its competitors’ products and processes, but the company also 

looked at other industries’ processes and translated those best 

practices into the Xerox standard procedures. Xerox defines 

benchmarking as “the continuous process of measuring our 

products, services, and practices against our toughest competitors 

or those companies known as leaders.”577 This model is comprised 

of ten steps in four phases: 

Planning phase 

Select a subject to benchmark

 Identify the best practitioners in the field of study 

Determine the data-collection method and collect the data 

Analysis phase

Determine the current gap

Project future performance

Integration phase 

Communicate the results of analysis

Establish functional goals

Action phase 

 Develop action plans 

 Implement plans and monitor results 

Recalibrate benchmark578

In the field of emergency medicine, efforts are underway to 

incorporate benchmarking.579 The non-profit Emergency 

Department Benchmarking Alliance spearheads this effort by 

maintaining a database of performance metrics, by hosting 

conferences and meetings, and by providing community-building 

services to their member organizations.580 According to the 

Alliance’s data, benchmarking seems to be working. Wait times in 

emergency departments from 2008 to 2009 fell for the first time in 

four decades.581 
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Violations 

Two types of violations deserve mention: willful noncompliance and exceptional violations. 

Often referred to as “bending the rules,” willful noncompliance tends to be habitual and is 

enabled by a system of supervision and management that tolerates departures from standard 

procedures. Just as some drivers may go 5 miles per hour over the speed limit, some examiners 

may engage in shortcuts to come to a conclusion. Exceptional violations are willful and

particularly egregious, and they are neither tolerated by management nor routinely observed in 

the forensic laboratory. An exceptional violation would be akin to driving 30 miles per hour over 

the speed limit. 

Examples of violations include deeming a latent print not suitable to avoid having to compare it, 

disregarding aspects of the QA/QC process (for example, skipping the Verification phase), 

intentionally misidentifying a latent print, making an identification or exclusion of a latent print 

that the examiner knows is not suitable for comparison, reporting results without conducting a 

comparison, and coercing a verifier into agreeing with a rendered conclusion. 

9.2.2 Conditions that Affect Performance

Conditions of the examiner, of communication, and of the environment can affect an examiner’s 

performance.

Physical and Mental State

An examiner’s mental state, physiological state, and physical or mental limitations all can affect 

performance. Adverse mental states include temporary conditions such as exhaustion and stress. 

The examiner and management should take appropriate action when the examiner is not fit for 

duty. In most forensic units, examiners confront large backlogs. Some examiners are held to 

quotas or unrealistic turn-around times. In this environment, examiners could become more 

concerned with case output than the quality of the work. As a result, examiners may hurry 

through cases, taking shortcuts in the analysis and documentation, and failing to reach an 

appropriate conclusion. Plainly, many factors can affect the mental state of the examiner. 

Examples are anger, apprehension about reaching conclusions, boredom and complacency, 

distraction, expectancy, fatigue, overconfidence, peer pressure, and personal problems. 

In addition, the examiner’s physiological state can affect the examination process. For example, 

the typical latent print examiner is usually bending over a desk or workbench for long stretches 

of time, looking through a magnifier, and making numerous comparisons. These working 

conditions produce strain on the neck, back, and eyes. Glare from computer displays and the 

sheer number of comparisons can result in headaches or eyestrain (see Chapter 7 for more 

information about healthy workplace design). 

Performance can also suffer due to lack of sleep. In many agencies, an examiner could be called 

to a crime scene in the middle of the night and then be expected to work a normal latent print 

caseload the next day without rest. Illness can have detrimental effects, and medications can 

influence a person’s quality of sleep and daytime alertness. Other factors bearing on 

physiological states include alcohol and drug use, nutrition, and injuries. 
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Finally, physical or mental limitations affect the condition of the examiner. Deteriorating 

eyesight is a physical limitation, while an inability to maintain competency is a mental limitation. 

If the physical or mental limitation cannot be compensated for, the examiner may no longer be 

qualified to perform latent print examinations. Other physical or mental limitations include 

chronic psychological disorders, dyslexia, inadequate training or experience, incompatible 

aptitude, and visual limitations such as poor acuity, poor contrast sensitivity, and color blindness. 

Communication 

An examiner must work with other examiners, management, investigators, attorneys, and 

administrative personnel. While verbal communication is certainly important, communication 

via case documentation is also imperative. Only with sufficient documentation and reporting can 

other examiners and supervisors adequately provide technical and administrative review. For 

instance, understanding the location, orientation, surface, and development technique of the 

latent print can be critical for interpreting print distortion. Additionally, understanding how the 

examiner searched the latent print (distal orientation and anatomical region) can provide critical 

information if an error has occurred. 

Communication can suffer from confusing or conflicting directions or demands, a failure to 

convey or obtain adequate information, lack of report-writing skills, lack of teamwork, poor case 

documentation, and departures from standard terminology. 

Environment 

Environmental factors can contribute to errors. Both the operational environment (e.g., 

workplace design or clutter) and the ambient environment (e.g., temperature, noise, and lighting) 

can degrade performance. For example, the intensity, type, and direction of lighting can 

influence what an examiner perceives as key data. Chapter 7 discusses such physical 

environmental conditions as clutter, excessive heat or cold, lighting, ventilation, and noise, as 

well as technical environmental factors such as equipment and software.

9.2.3 Supervisory Issues

If an error has occurred, the investigation of the cause(s) starts with the examiner’s actions, 

proceeds through the conditions that may have contributed to the error, and continues on to 

supervisory actions and possibly organizational oversights or failures. 

Leadership 

Effective management provides examiners with adequate training, professional guidance, 

oversight, and operational leadership. Without this leadership, the chance of errors is greater. 

Managers can become so overwhelmed with meetings and paperwork that they fail to provide 

sufficient oversight. Yet, some supervisors take oversight to extremes, becoming too controlling 

and more concerned with minute details than the accuracy of the work. Micromanaging 

examiners can delay decision-making, restrict information flow, and diminish confidence and 

efficiency. 

Effective leadership helps avoid errors by ensuring appropriate training; setting a proper 

example; tracking and assessing job qualifications or skills; monitoring work; providing 

appropriate feedback, mentoring, and incentives; and maintaining realistic expectations. 
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Operational Planning 

Management is responsible for planning the operations of the forensic unit. Scheduling should 

include breaks and should take caseloads and deadlines into account. The supervisor who assigns 

a large complex case to a less experienced examiner may inadvertently set up the examiner for 

failure. Conversely, burdening the top performers with excessive work can keep them from 

performing optimally and can limit the opportunities for less experienced examiners to learn. 

Many latent print units are so overwhelmed that supervisors must divide casework into rush 

cases and routine ones. Examiners with many rush cases can feel overwhelmed, frustrated, and 

confused. Supervisors and managers need ways to allocate casework to maintain productivity 

without causing frustration. Allowing examiners to finish one batch of cases before assigning 

another batch can be helpful. Also, management can sometimes request a certain amount of time 

from the court for rush cases to ensure that examiners can work the case properly. Trials can 

even be rescheduled, if necessary. Other examples of operational planning failures are not 

allowing adequate rest breaks; setting conflicting objectives, goals, or standards; and giving 

unclear or conflicting assignments.

Problem Correction 

When problems are known, they should be corrected. Consistent failure to correct or discipline 

inappropriate behavior may foster a dysfunctional work environment. This caution also applies 

to issues associated with equipment and supplies. When necessary repairs are overlooked or 

supplies do not meet specifications, errors can result. 

Supervisory Violations 

Supervisory violations encompass the disregard of existing rules and regulations. An obvious 

example of poor supervisory behavior is putting undue influence on an examiner to reach a 

desired result. A more subtle violation is permitting an unqualified examiner to perform 

casework. Likewise, pushing an examiner to work unreasonably fast or encouraging “bending 

the rules” and procedures in the interest of completing a case are poor supervisory actions. 

9.2.4 Organizational Influences

Organizational influences are the fourth and final layer—the last slice of Swiss cheese—to 

investigate when evaluating the factors that led to an error. Three areas of organizational failures 

fall into this category: resource management, organizational climate, and operational processes.

Resource Management 

Resource management refers to the management, allocation, and maintenance of organizational 

resources, including human resource management (selection, training, staffing), budgets, 

logistics, and equipment design. Management decisions about such resources should focus on 

both quality and cost-effectiveness. Unfortunately, quality improvements and training are often 

the first items to be cut when experiencing financial difficulty. Resource management issues 

include maintaining hiring, evaluation, and promotion policies; matching qualifications to job 

assignments; reducing costs and managing unfunded directives; providing logistical support; and 

making suitable equipment available. 
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Organizational Climate 

Organizational climate influences 

examiner performance. The structure 

of the organization includes the 

chain of command, delegation of 

authority and responsibility, 

communication channels, and formal 

accountability for actions. Agency 

policies that are ill defined, 

adversarial, conflicting, or 

supplanted by unofficial rules and 

values can cause confusion, reduce 

quality, and lead to a negative 

organizational climate. 

Inaccessibility of upper 

management, inadequate 

accountability for actions, poorly 

defined or articulated organizational 

values, inappropriate allocation of 

resources, and unclear or conflicting 

assignments of responsibility can 

also lead to a negative organizational 

climate. 

Many analysts work in fear of 

retribution from management, coworkers, and the International 

Association for Identification (IAI) 

Certification Board should they 

misidentify a print. The IAI 

Certification Program Operations Manual states that a technical error may result in suspension 

or revocation of certification and that the IAI can publish the results of any disciplinary action. 588 Consequently, some examiners may be unable or unwilling to make difficult identifications. 

Worse yet, examiners may feel compelled to conceal mistakes. 

 

582 Roberts, K. and R. Bea. “Must Accidents Happen? Lessons from High-Reliability Organizations.” Academy of 

Management Executive, 15, no. 3 (2001): 70. 583 Roberts, K. “Some Characteristics of One Type of High Reliability Organization.” Organization Science, 1, no. 2 

(1990): 160. 584 Baker, D., R. Day, and E. Salas. “Teamwork as an Essential Component of High-Reliability Organizations.” 

Health Services Research, 41 (August 2006): 1576–98.

585 Dyck, L. “High Reliability Organization (HRO) in Practice.” Technical Support. January 2007. 586 Rochlin, G. “Defining ‘High Reliability’ Organizations in Practice: A Taxonomic Prologue.” In New Challenges 

to Understanding Organizations. Macmillan, 1993.

587 Roberts and Bea, op. cit. 588 International Association for Identification. Certification Program Operations Manual. Version 2010_H_I. 

International Association for Identification, July 10, 2010.

Box 9.2: High-Reliability Organizations

High-reliability organizations (HROs) are those with tightly 

coupled, complex systems that have many potential points of 

failure, any of which could result in catastrophic damage.582

Traditionally, these organizations are thought to include 

nuclear power plants, air traffic control centers, aircraft 

carriers, and submarines,583 but many habits of HRO 

managers can benefit forensic science. While operating in a 

highly complex environment, notably few catastrophic 

failures occur in a successful HRO. For example, hospitals 

consist of many individuals at many hierarchical levels 

contributing to life-or-death decisions. To improve this 

process in all hospitals, the Agency for Healthcare and 

Research Quality has established an HRO network to allow 

personnel to learn from each other’s expertise.584

Effective HROs empower employees at all levels with “a way 

of looking at your job and your environment in a ‘mindful’ 

way, which basically means that you both anticipate potential 

problems and that you are also prepared for them should they 

occur.”585 In other words, staff members should consider 

things that could go wrong and strive to improve on the status 

quo.586 Staff members must be trained to recognize and 

address anomalies in the system and should be rewarded for 

doing so. The overall mission, communicated clearly 

throughout the organization, must be willing to balance 

short-term gains with long-term reliability.

587 Management 

cannot take steps to “cut corners” without expecting a system 

failure. 
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Effective management is vital to delivering high-quality forensic services. Because human error 

in interpreting forensic science evidence can have devastating effects, examiners should be 

encouraged to come forward to help understand when and why errors occur. Management must 

foster a culture that promotes openness and acceptance when errors are committed without 

fostering a nonchalant attitude. The Working Group recommends: 

Recommendation 9.1: Management should foster a culture in which it is understood 

that some human error is inevitable and that openness about errors leads to 

improvements in practice. 

Operational Processes 

Operational processes refer to formal processes (e.g., operational tempo, time pressures, 

production quotas, incentive systems, and schedules), procedures (e.g., performance standards, 

objectives, documentation, and instructions about procedures), and oversight within the agency 

(e.g., organizational self-study, risk management, and establishment and implementation of a 

QA/QC process). Poor upper-level management decisions concerning each of these factors can 

also have a negative effect on the examiners’ performance. Operational process factors include 

accreditation; appropriate standards, policies, or guidelines; documentation for standard 

operational procedures; overextension of resources; procedures that are not integrated into the 

training process; and, again, work and production schedules that produce risky decisions. 

Recommendation 9.2: Management should employ a system to identify and track errors

and their causes.

Appendix A gives a sample taxonomy of human factors issues and errors, including those 

discussed above. Appendix B includes an example of a Corrective Action Report, and Appendix 

C shows how the human factors described in the chapter apply to that particular error. 

9.3 Accreditation as a Means to Quality Improvement

Accreditation is a multi-faceted process that ensures that the forensic laboratories follow a 

documented quality management system and adhere to standards of operation promulgated 

through standard-developing organizations. An accrediting body’s routine onsite surveillance 

visits, required annual self-audit reports, and an externally monitored proficiency testing 

program assures periodic monitoring of the unit’s compliance with the accreditation program’s 

requirements.

Through accreditation, a forensic service provider demonstrates compliance with nationally and 

internationally recognized standards. Accreditation also ensures that the forensic unit has 

procedures in place to take appropriate corrective actions when indications of a significant 

problem appear. Unfortunately, there is a lack of uniformity in the application of existing 

accreditation standards in the United States, and different accrediting organizations apply 

different requirements (see Chapter 8). 
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9.3.1 Personnel Requirements

Personnel requirements for accreditation 

include minimum standards for education, 

training, competency testing, and ongoing 

proficiency testing. Before assuming 

casework responsibility, each examiner 

should complete an established training 

program and should be tested for 

competency, at least in the most relevant 

work areas. Examiners should be routinely 

reviewed through annual proficiency testing, 

technical review of reports and examination 

records, and annual courtroom testimony 

monitoring (see Recommendation 6.4). 

Ongoing professional development for each 

examiner is an important element of the 

accreditation process.

Under the International Organization for 

Standardization’s international standard 

ISO/IEC 17025, a forensic unit “must have 

arrangements to ensure that its management 

and personnel are free from any undue 

internal and external commercial, financial, 

and other pressures and influences that may 

adversely affect the quality of their work.”590

9.3.2 Management Procedures

Accreditation requires documented quality management procedures for the operation of the unit. 

The management system must designate a quality manager responsible for ensuring that the unit 

operates in conformity with the quality management system. Procedures must include steps to 

ensure that evidence is protected from loss, cross-transfer, contamination, or deleterious change. 

The procedures must ensure that evidence is properly marked and tracked throughout the period 

the unit controls the evidence. 

9.3.3 Technical Procedures

Technical procedures must be documented, validated, and accepted in the scientific community. 

An accrediting agency conducts onsite assessments to ensure that the unit follows its 

documented procedures, adheres to the required standards, and uses proper controls. 

 

589 Council Framework Decision 2009/905/JHA of 30 November 2009 on Accreditation of Forensic Service 

Providers Carrying out Laboratory Activities. “Acts Adopted Under the Title VI of the EU Treaty.” Official Journal 

of the European Union, 52, (December 9, 2009): 14–16.

590 International Organization for Standardization. General Requirements for the Competence of Testing and 

Calibration Laboratories, ISO/IEC 17025:2005(E). 2nd ed. International Organization for Standardization, 2005.

Box 9.3: Accreditation in the European 

Union

In late November 2009, the European Union (EU) 

approved a measure known as the Framework 

Decision to standardize forensic laboratory 

accreditation in member states. Because of the high 

likelihood for cross-border crimes in the EU, 

judicial systems in each country must have 

confidence in laboratory results from other 

countries. 

The standards require national accreditation bodies 

in each member state to grant accreditation to 

forensic laboratories that comply with ISO/IEC 

17025, General requirements for the competence of 

testing and calibration laboratories. The 

accreditation standard specifically applies to 

laboratories that produce DNA profiles or work with 

latent print data. Each member state is responsible 

for ensuring compliance, for granting accreditation 

to their own laboratories, and for providing any 

funding necessary to achieve accreditation. The EU 

requires all latent print labs to comply with ISO/IEC 

17025 by November 30, 2015.589 
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9.3.4 Facility Safety and Security

The forensic unit should have a well-designed, efficient laboratory with adequate ventilation and 

safety equipment. All forensic units should follow applicable Occupational Safety and Health 

Administration standards, state and local health agency guidelines, and other safety regulations 

and should offer a mandatory safety training program (see Chapter 7). 

The facility must have security to limit access to evidence, whether stored or under examination, 

and access to authorized individuals. The accreditation process evaluates the physical plant to 

ensure these standards are met. 

Recommendation 9.3: All forensic service providers should be accredited by a 

recognized accrediting body.

9.4 Case Review, Conflict Resolution, and Corrective Action

Assuring the quality of forensic work, particularly in those disciplines in which the examiner is 

the sole provider of the results, can be challenging. Examiners can be influenced by a range of 

factors, including experience, fatigue, and stress. Not only are no two examiners exactly alike, 

but also an individual examiner’s performance level can vary throughout the day. Thus, case 

review is an integral component of quality management.591 

Case review involves verification, technical review, and administrative review. During the 

Verification phase of the Analysis, Evaluation, Comparison, and Verification process, a second 

examiner re-examines the latent prints to confirm or refute the conclusion of the case examiner. 

During technical review, another expert reviews the case file and report “to ensure the validity of 

scientific results and conclusions.”592 During administrative review, an expert examines the case 

file “for consistency with laboratory policy and for editorial correctness.”593 If discrepancies 

arise, the laboratory must have policies and procedures in place to address them.594 Numerous 

discrepancies can arise, but the remainder of this section focuses on disagreements during 

Verification, methods to resolve conflicting results, and corrective action. 

9.4.1 Verification

Agencies should have a clear policy indicating which results will undergo verification. The 

Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) 

quality assurance guidelines state that source attributions “shall be verified prior to reporting” 

 

591 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Quality Assurance Guidelines for 

Latent Print Examiners. Version 3.0. Scientific Working Group on Friction Ridge Analysis, Study and Technology, 

September 2006.

592 American Society of Crime Laboratory Directors/Laboratory Accreditation Board. ASCLD/LAB-International 

Supplemental Requirements for the Accreditation of Forensic Science Testing Laboratories 2011 Edition. American 

Society of Crime Laboratory Directors/Laboratory Accreditation Board, approved September 11, 2010.

593 Ibid.

594 SWGFAST, 2006, op. cit.
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but that “exclusion or inconclusive results may be verified.”595 Verifying all results would be 

ideal (and some agencies do so). To conserve resources, however, agencies may verify all 

identifications but only a portion of the exclusions and inconclusive results. 

The verifier typically receives the latent prints, the exemplar prints, the conclusions of the case 

examiner, and other information. In a blind verification, however, the verifier does not know the 

outcome of the first examination (see Chapters 1, 3, and 5). For blind verification to be 

meaningfully conducted, a sufficient proportion of all case conclusions must be reviewed. 

SWGFAST has released a Standard for the Application of Blind Verification of Friction Ridge 

Examinations596 to assist agencies instituting blind verification.597 Additional research into the 

costs and benefits of blind verification would be valuable. 

9.4.2 Conflict Resolution

Once the agency establishes procedures for verifications, it also must adopt procedures for 

handling and documenting conflicting decisions. Conflict can occur because examiners have 

varying degrees of knowledge, skills, training, and experience. The agency must have a method 

to determine the result that will be reported as correct. Some agencies have a technical leader 

who makes the final decision. Others use a panel of examiners. Still others send conflicting 

results to another forensic service provider, which helps to mitigate some internal concerns (e.g., 

systemic error, personality conflicts, and bias) but is not practical for all agencies. Regardless of 

the procedure implemented by the agency, the existence of the disagreement should be noted in 

the report, and the basis for the final consensus should be stated in the report or other 

documentation. (For additional discussion of conflict resolution and how it differs from 

consultation, see Chapter 5, section 5.3.5.) 

9.4.3 Corrective Action

Once the conflict has been resolved, an “error” will have to be attributed to either the case 

examiner or the verifier, and corrective action may be appropriate.598 For instance, failing to 

identify a single latent print on an item when the subject has been identified as leaving other 

prints on the item may not be critical. An occasional non-critical failure to identify does not 

necessitate a formal corrective action; however, routine failures to identify should result in a 

formal corrective action, as it may indicate a contributing issue such as training, medical issues, 

or the work environment. Regardless of any formal corrective actions, management should track 

errors to determine if there are chronic problems. 

 

595 Ibid. (emphasis added).

596 Scientific Working Group on Friction Ridge Analysis, Study and Technology. Standard for the Application of 

Blind Verification of Friction Ridge Examinations. Version 1.0. Scientific Working Group on Friction Ridge 

Analysis, Study and Technology, February 2011. 597 For discussion of a mixed system of blind and non-blind verification, see U.S. Department of Justice, Office of 

the Inspector General. A Review of the FBI’s Progress in Responding to the Recommendations in the Office of the 

Inspector General Report on the Fingerprint Misidentification in the Brandon Mayfield Case. U.S. Department of 

Justice, 2011.

598 SWGFAST, 2006, op. cit.
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The response of management to an error must be commensurate with the potential impact and

frequency of the error.599 When errors occur, resolution may involve a simple consultation 

between the examiners or a formal corrective action. ISO/IEC 17025 accreditation standards 

state that (1) a laboratory must have policies and procedures regarding the implementation of 

corrective action, (2) the procedures must include an investigation to determine root causes, and 

(3) the laboratory must take preventive measures to mitigate the problem.600 Appendix B 

provides a sample Corrective Action Report, which describes the circumstances of an error, the 

corrective action, and the preventive measures. 

Appendix C lists the human factors issues from all levels (examiner, conditional, supervisory, 

organizational) that contributed to the error in Appendix B. By compiling statistics on the 

various human factors issues related to each error, evaluating the data from multiple errors, and 

looking for common themes, management can become aware of critical failures in the system 

that could be setting the examiners up for failure. This systems approach could improve 

examiner performance not only within an agency but also throughout the profession. 

Recommendation 9.4: Management should establish policies and procedures for case 

review and conflict resolution, corrective action, and preventive measures. 

9.5 Competency, Certification, and Proficiency Testing

Certification and testing for competency and proficiency are components of a strong 

quality management system. Testing is one way to measure the examiner’s knowledge, 

skills, and abilities. It can be used to demonstrate the examiner’s minimum competency, 

achievement of proficiency, and continued proficiency. A competency test evaluates “a 

person’s knowledge and ability prior to performing independent casework.”601 A 

proficiency test evaluates “the capability and performance of analysts, technical support 

personnel, and the laboratory; in open tests, the analysts and technical support personnel 

are aware that they are being tested; in blind tests, they are unaware.”602

Many professions (e.g., language training, medicine, accountancy, and law) use testing and 

certification to demonstrate and acknowledge that an individual has met established minimum 

standards of skills and knowledge. In these professions, the testing process is typically called 

competency testing, and the official acknowledgement is called certification. Various professions 

handle certification and proficiency testing in different ways. 

 

599 Ibid.

600 ISO/IEC 17025:2005(E), op. cit. 601 ASCLD/LAB, op. cit.

602 Ibid.
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The process of competency 

testing, certification, and 

proficiency testing in the latent 

print discipline is largely ad hoc 

by jurisdiction and agency. It 

may be difficult to gain 

consensus on what competency, 

certification, and proficiency 

mean, let alone how they will be 

attained or documented. Yet, 

accreditation standards require 

competency testing prior to 

performing casework and the 

successful completion of a 

proficiency test by each 

examiner annually. 

Recommendation 9.5: The 

latent print community 

should develop and 

implement a comprehensive 

testing program that 

includes competency 

testing, certification testing, 

and proficiency testing. 

A standardized national testing 

program would be very useful in 

achieving this goal. To 

implement such a program, 

however, major tasks would need 

to be accomplished. Research should evaluate current training programs to discern similarities, 

weaknesses, and effectiveness (see Chapter 8). Training standards and standardized training 

material, including practical exercises, should be written, and criteria for selecting qualified 

trainers should be developed. A standardized test should be written with input from specialists in 

test design and validation. This test (or others) could be part of the framework for comprehensive 

testing described below. 

9.5.1 Competency Training

During the training program, the new examiner should work toward a minimum level of 

knowledge and skill. To show that this level has been achieved, the examiner should pass a 

standardized competency test. Because examiners typically perform additional agency-specific 

functions (e.g., automatic fingerprint identification system entry, latent print development, and 

latent print photography), the agency or a national body should develop competency tests 

tailored to the examiner’s duties.

Box 9.4: Certification and Testing for the Practice of 

Medicine

Upon graduation from an accredited medical school, all medical 

school graduates are required to pass a national licensing 

examination before practicing medicine. The test is sponsored by 

the Federation of State Medical Boards and the National Board of 

Medical Examiners. The first part (on anatomy, physiology, 

biochemistry, pharmacology, pathology, microbiology, and 

behavioral sciences) typically is taken at the end of the second 

year of medical school. The second part (on clinical knowledge),

includes demonstrations of clinical skills via simulated patient 

encounters and typically is taken in the fourth year of medical 

school. The final part is taken at the end of the student’s formal 

medical school training and before internship and residency. This 

2-day test measures the student’s knowledge of basic science and 

medicine and assesses his or her ability to manage patient care via 

case simulations that include prescribing medications. 

After completing formal medical education at an accredited 

medical university and passing the competency examinations, 

U.S. medical students are required to complete a 1-year 

internship. This internship is typically part of the student’s 

postgraduate residency in a chosen specialty (e.g., orthopedics, 

radiology, family practice). The internship is the minimum 

training requirement for a license to practice medicine in the U.S. 

and for taking most state medical board certification tests. All 

state medical specialties require periodic proof of continued 

professional competency. Continued professional competency 

often includes continuing medical education, recertification 

examinations, and some measure of clinical skills as approved by 

the certification board. 
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After succeeding in the competency tests, an examiner can perform casework. A certified 

examiner should review the new examiner’s casework at this stage. All conclusions should be 

verified, and each case should undergo technical review. This verification and technical review 

should continue until the agency determines that the examiner can work successfully under the 

agency’s routine verification and technical review process. The examiner should not perform 

verification or technical reviews before becoming certified. 

9.5.2 Certification Testing

A standardized certification test demonstrates that the examiner has become proficient in 

casework and meets or exceeds minimum competency to perform latent print examinations. To 

retain certification, an examiner should complete continuing education requirements and 

demonstrate proficiency in periodic proficiency tests. 

9.5.3 Proficiency Testing

Periodic proficiency tests are a means to ensure that examiners maintain their skills. Agencies 

should administer proficiency tests at least annually that reflect the type of casework performed 

by the examiner. A standardized proficiency test for each examiner not only could demonstrate 

the necessary ability to continue as an examiner, but it also could inform training needs across 

the discipline. For instance, a high erroneous exclusion rate on latent palm prints that lack a clear 

distal orientation and anatomical region could indicate that training programs need to place more

emphasis on palm prints or that examiners need periodic refresher training on palm prints.603

9.6 Summary

This chapter offers recommendations about the principles, policies, and practices of management 

and describes strategies to prevent human errors in latent print examinations. Management 

within any forensic operation must be committed to developing, maintaining, and improving 

quality assurance and quality control. Latent print units should report accurate and timely results. 

The examiners have the responsibility to provide results and testimony based upon scientific or 

technical knowledge, training, and experience. Management must create the proper environment 

for this to occur. This includes creating an impeccable QA/QC process; meeting standards of 

certification, accreditation, and proficiency testing; and adopting a systems approach to reducing 

errors.

 

603 Proficiency testing for other purposes, such as estimating error rates, is considered in Chapter 2.
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Appendix 9-A: Sample Taxonomy of Errors and Human Factors

The following tables contain a classification scheme that outlines potential sources of error. 

Additional factors at every level could always occur and should be documented and tracked. 

Examiner Actions

Decision-Based Mistakes

Conclusion exceeded ability of examiner

Failure to recognize exemplars as inadequate

Failure to search all exemplars

Failure to use available technology

Hurried or insufficiently thorough examination

Improper anatomical source of data

Improper orientation of images

Incomplete search

Insufficient data to support conclusion

Mis-prioritized level of effort

Poor target group selection

Print improperly deemed suitable

Print improperly deemed unsuitable

Perception-Based Mistakes

Not all data perceived

Data perceived and compared inadequately

Skill-Based Mistakes

Failure to find target data

Failure to properly weight the significance of the 

data

Failure to recognize distortion

Inability to reach a conclusion

Incomplete comparison

Misinterpreted data

Not all data understood

Poor search technique

Examiner Violations

Deeming a latent print not suitable intentionally

Disregarding QA/QC procedures (e.g., verification)

Disregarding discrepant information

Erroneously identifying a latent print (intentionally)

Identifying an unsuitable latent print (intentionally)

Including a subject inappropriately (intentionally)

Misrepresentation of information

Not comparing a latent print and reporting exclusion 

or inconclusive results

Seeking/coercing another examiner to verify a 

complex comparison
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Conditions That Affect Performance

Adverse Mental States of the Examiner

Anger

Apprehension to reach a conclusion

Bias 

Boredom

Channelized attention

Complacency

Compromised integrity or ethics

Distraction

Expectancy

Frustration

Haste

Lack of confidence

Mental fatigue

Misplaced motivation

Overconfidence

Peer pressure

Preoccupation with personal problems

Task overload

Stress

Adverse Physiological States of the Examiner

Alcohol use (intoxicated or hung-over)

Eyestrain

Illicit drug use

Inadequate nutrition (poor dietary practices)

Lack of sleep

Medical illness

Physical fatigue (e.g., postural fatigue)

Physical injuries

Medication side effects

Physical or Mental Limitations of the Examiner

Chronic psychological disorder

Color vision deficiency

Dyslexia

Inadequate training

Incompatible intelligence/aptitude

Limited experience

Visual limitations (e.g., acuity or contrast sensitivity)

Communication

Confusing or conflicting directions or demands

Failure to convey adequate information

Failure to use all available sources of information

Inadequate communication among examiners

Inadequate communication with management

Inadequate report writing skills

Inadequate teamwork

Inadequate case documentation

Standard terminology not used

Physical Environment

Clutter

Excessive heat or cold

Inadequate lighting

Inadequate ventilation

Poor workplace design

Noise interference

Technical Environment

Defective equipment

Defective tools

Inadequate/outdated software or equipment
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Supervisory Issues

Leadership Failures

Change induced without training

Failure to provide professional guidance and 

oversight

Failure to set proper example

Failure to track job qualifications or skills

Inadequate assessment of required skill

Inadequate leadership job knowledge

Inadequate monitoring of work

Inadequate or incorrect performance feedback

Inadequate performance measurement or evaluation

Insufficient initial or ongoing training provided

Inadequate or inappropriate incentives

Inadequate coaching or mentoring on skill

Inadequate measurement of training effectiveness

Personality conflicts 

Unrealistic expectations

Operational Planning Failures

Excessive workload

Failure to provide adequate rest breaks

Improper or insufficient delegation of work

Inadequate communication of policy, procedure, 

practices, or guidelines

Inadequate documentation

Inadequate matching of individual qualifications and 

job or task requirements

Setting objectives, goals, or standards that conflict

Unclear or conflicting assignment of responsibility

Unrealistic deadlines or quotas

Failure to Correct Known Problems

Failure to correct inappropriate behavior

Failure to correct reported problem

Failure to correct workplace hazards

Failure to initiate corrective action

Failure to update standard operating procedures

Rewarding or tolerating improper performance

Supervisory Violations

Enabling excessive risk-taking

Failure to enforce rules and regulations

Supervisor encouragement of rule bending

Fraudulent documentation

Management-induced haste

Unrealistic production goals

Undue influence toward a desired outcome

Violation of standard operating procedures by 

supervisor
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Organizational Influences

Resource Management Failures

Failure to correct known design flaws

Inadequate evaluation and promotion policies

Inadequate hiring, firing, and promotion processes

Inadequate matching of qualifications for the job 

Ineffective cost-cutting

Lack of logistical support

Purchasing unsuitable equipment/parts

Inadequate selection of personnel

Inadequate staffing

Use of inadequate contractor or vendor

Unfunded directives

Organizational Climate Failures

Inadequate accessibility or visibility of upper 

management

Inadequate allocation of resources

Inadequate formal accountability for actions

Dysfunctional organizational culture

Organizational values not clearly defined and 

articulated

Unclear or conflicting assignments of responsibility

Operational Process Failures

Failure to maintain accreditation 

Lack of appropriate standards, policies, or guidelines

Inadequate documentation for standard operating 

procedures

Organizationally induced time pressure

Overextending resources

Procedures not integrated into training process

Quality process not adequately implemented or 

maintained

Unrealistic quotas established by the organization

Work or production schedules that produce risky 

decisions
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Appendix 9-B: Corrective Action Report Sample

FORENSIC LAB CORRECTIVE ACTION REPORT

Place “N/A” in blanks that are not applicable.

APPLICABLE #(S) (e.g., Event #, CTS #) RELEVANT INSTRUMENT:

Case: 12356-78 Instrument type: N/A

Manufacturer: N/A

Model #: N/A

Serial #: N/A

DESCRIPTION OF INCIDENT/EFFECT OF DISCREPANCY

Forensic scientist (FS) Jane Doe was assigned homicide case #123456-78. FS Doe worked the case during 

November and early December 2010. FS Doe completed the initial formal report in December 2010. She 

developed latent prints on 4 items of evidence and recovered 16 latent prints. She deemed two of these suitable 

for comparison. FS Doe also examined 3 latent print packets submitted by Crime Scene Examiners (CSEs), 

containing 56 lifts/photos. On these lifts/photos, 75 suitable latent prints were present.

FS Doe compared the 77 suitable latent prints to those of 5 suspects, 1 victim, and 1 other subject identified via 

the automated fingerprint identification system (AFIS). This amounts to 539 conclusions. One suspect was 

identified to one of the latent prints recovered from the evidence. Another suspect was identified to one latent 

print submitted by the CSEs. The AFIS subject was identified to 28 latent prints submitted by the CSEs.

Manager Susan Smith verified these results on February 4, 2011. Manager Smith noted that two of the 

identifications recorded by FS Doe were to the incorrect finger of the correct subject (AFIS subject). FS Doe 

originally identified the two latent prints to the right thumb of the subject; however, one was made by the right 

middle finger, and the other was made by the right ring finger of the same subject. 

Manager Smith noted the correct conclusion in the case notes and asked FS Doe to review her conclusions. FS 

Doe immediately noticed the errors. Manager Smith verbally notified the quality assurance (QA) manager and 

the laboratory director on February 8, 2011. The case was returned to FS Doe, and she created charted 

enlargements for her case file and annotated the notes appropriately. Manager Smith completed a technical 

review of the case on February 25, 2011, and issued the report. 

There was no effect of the discrepancy, as the errors were caught during the Verification phase.

Date: 3/4/11 Reported By: Manager Smith
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ROOT CAUSE DETERMINATION

The right thumb, middle, and ring fingers of the subject had similar ridge configurations in the core. The similar 

pattern, ridge count, and ridge configuration in these fingers likely contributed to the errors. 

In addition, FS Doe was under significant stress during this time period because of the terminal illness of a 

parent. 

FS Doe also indicated to Manager Smith that she was trying to increase her case productivity to help alleviate 

the backlog. The pressure FS Doe was placing upon herself to complete the case may also have contributed to 

the error.

FS Doe was increasing the use of fingerprint loupes into the analysis of her casework during this time period to 

prepare for the International Association of Identification (IAI) Latent Print Certification Test. This was a 

significant departure from her normal routine, which focuses on the use of digital imaging during her 

comparisons. (The IAI certification test does not permit use of digital imaging technology.) FS Doe normally 

charts her identifications via Photoshop, but she did not do so in this case because she used the loupes.

The cumulative effect of the stress of life events, similarity of the prints, time pressure, and technology 

adaptations ultimately resulted in these errors.

Determined By: Manager Smith

CORRECTIVE ACTIONS AND PREVENTIVE MEASURES TAKEN

Corrective Action

FS Doe was placed on supervised casework for a period of 30 days. Nine cases were fully reviewed and reexamined during this time. No errors were noted. Upon completion of the 30 days of supervised casework, FS 

Doe was assigned a Collaborative Testing Services test as in-house proficiency test on March 17, 2011. FS Doe 

successfully completed this test on April 1, 2011.

From November 1, 2010, to February 3, 2011, FS Doe completed 10 cases. Seven of these cases were reviewed. 

No errors were noted on the identifications in these cases. The three cases that were not reviewed during this 

time were latent print development cases, and no comparable latent prints were recovered.

Preventive Measures

FS Doe and Manager Smith analyzed and marked 30 difficult latent prints to evaluate FS Doe’s ability to 

interpret and detect minutiae. Once marked, FS Doe and Manager Smith compared the markings and discussed 

the results for each image. The goal of this exercise was to ensure that FS Doe was correctly assessing friction 

ridge detail. FS Doe successfully completed this exercise: Manager Smith did not note any problems with FS 

Doe’s interpretation of the friction ridge detail.

The Forensic Laboratory monitors the caseload and work product more carefully during high-stress times. Over 

time, examiners learn when they are not mentally able to perform the task and postpone the examination to a 

better time. Possibly, cases should be re-assigned in this situation.

If FS Doe chooses to use the fingerprint loupe in casework, the comparison will be repeated utilizing digital 

imaging to determine if the re-examination yields any inconsistencies.

Date: 5/3/2011 Approved By: QA Manager
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ROUTE TO IN LAB: (NAME & P #) SIGNATURE DATE

FS Jane Doe

Manager Smith

QA Manager

Laboratory Director

ADDITIONAL NOTIFICATIONS, IF REQUIRED:

PERSON NOTIFIED: (NAME & TITLE / P #) DATE NOTIFIED

ASCLD/LAB Notified: □ Yes X Not Required

NOTES:

Jane Doe has not made any erroneous identifications since this incident - QA Manager 8/26/2011

THIS SECTION WILL BE COMLPETED BY THE QUALITY ASSURANCE MANAGER

Was the problem corrected? × Yes □ No (if no, complete section below)

FOLLOW-UP, IF REQUIRED:

N/A - QA Manager
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Appendix 9-C: Applying Human Factors to an Error

Human factors issues have an impact on examiner performance. The error described in the 

Corrective Action Report (CAR) in Appendix B was the culmination of a breakdown in the 

system, not just the fault of the examiner. The examiner involved is a dedicated professional and 

an excellent casework examiner. In reviewing the CAR, one can look at the various holes in the 

Swiss cheese model at each level: Examiner Actions, Conditions that Affect Performance, 

Supervisory Issues, and Organizational Influences.

Examiner Action: Decision-Based Mistakes Supervisory Issues: Leadership Failures

Failure to use available technology Inadequate assessment of required skill

Hurried or insufficiently thorough examination Inadequate monitoring of work

Miss-prioritized level of effort Inadequate coaching or mentoring on skill

Examiner Action: Skill-Based Mistake Organizational: Resource Management Failures

Misinterpreted data Inadequate staffing

Examiner Action: Perception-Based Mistake Organizational: Operational Process Failures

Not all data perceived Organizationally induced time pressure

Overextending resources

Conditions: Adverse Mental States

Preoccupation with personal problems

Stress
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Chapter 10: Summary of Recommendations 

The recommendations and suggestions of the Working Group address issues ranging from the 

acquisition of impressions of friction ridge skin to courtroom testimony, from laboratory design 

and equipment to research into emerging methods for associating latent prints with exemplars. 

This group is not the first to address most of these matters; the recommendations are informed by 

and build upon the work of many practitioners and scholars of forensic science and evidence as 

well as the experience of other industries and enterprises that must deliver safe products or 

services. This concluding chapter collects and organizes the recommendations put forth on the 

following topics: 

• Performing Analysis, Comparison, Evaluation, and Verification (ACE-V)

• Reporting and testifying

• Managing the process 

• Improving training and education 

• Providing facilities and equipment 

• Supporting research efforts

10.1 Performing Analysis, Comparison, Evaluation, and 

Verification (ACE-V)

Latent print examinations can produce very powerful evidence regarding the possible association 

between a suspect and the source of a print. The long-established practice in latent print 

examinations is to interpret the evidence in terms of the categorical conclusion that two prints do 

or do not share a common source (or to report that the information presented does not permit 

such a categorical conclusion). Traditionally, a fingerprint identification was considered an 

“individualization,” meaning that the latent print was considered identified to one finger of a 

specific individual to exclude every other potential source in the universe. However, this claim is 

needlessly strong, not yet adequately supported by fundamental research, and impossible to 

validate solely on the basis of experience. Nor does fingerprint evidence have objective standards 

or a well-validated statistical model that can provide an objective measure of its strength in a 

given instance. Therefore, examiners should not claim to be able to exclude every other finger in 

the world as a potential source. Rather, an identification decision suggests a substantial enough 

similarity that, based on the examiner’s training and experience, the examiner believes that the 

two impressions originated from a common source. Whether any other finger in the entire world 

might also be able to leave an impression with a comparable amount of similarity is not fully 

known, and the examiner’s testimony should not suggest otherwise. Regardless of the specific 

words used to describe an identification, examiners should refrain from claiming that an 

identification means that they have excluded all other individuals in the world. 

Because empirical evidence and statistical reasoning do not support a source attribution to 

the exclusion of all other individuals in the world, latent print examiners should not report or 

testify, directly or by implication, to a source attribution to the exclusion of all others in the 

world. (Recommendation 3.7)
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The alternatives to the theory of universal individualization include probabilistic forms of source 

attribution (see Chapter 1), qualitative or quantitative likelihood ratios (determined subjectively 

or, in the future, with probabilistic models, as discussed in Chapters 4 and 6), or a broader range 

of conclusions than the three choices of identification, exclusion, or inconclusive. Without taking 

a position on which of these approaches is best, the Working Group recommends: 

The friction ridge examiner community and other experts should determine under what 

circumstances a qualified rather than an absolute conclusion is warranted. (Recommendation 

3.8) 

However the conclusion of a latent print examination might be framed, the examination process 

requires the careful interpretation and comparison of friction ridge impressions. From the first 

examination of the features contained in a latent print to a final conclusion regarding an 

identification or exclusion, an examiner engages in many acts of interpretation. Current methods 

for making these interpretations are based on professional knowledge and experience rather than 

on formal decision thresholds or statistical models. The process known as ACE-V organizes the 

interpretations and decisions of an examiner into a useful and logical sequence, but descriptions 

of this process do not detail the substantive content of the various steps. Examining latent prints 

and exemplars necessitates judgment and expertise, which inevitably makes the interpretive 

process partly subjective. With this subjectivity of interpretation comes the possibility of reduced 

performance due to a wide range of human factors issues. To increase the transparency of the 

process and to insulate the examiner from extraneous influences, the Working Group makes the 

following recommendations: 

A report and contemporaneous supporting notes or materials should document the 

examination to make the interpretive process as transparent as possible. Although the degree 

of detail may vary depending on the perceived complexity of the comparison, documentation 

should, at a minimum, be sufficient to permit another examiner to assess the accuracy and 

validity of the initial examiner’s assessment of the evidence. (Recommendation 3.1) 

Modifications to the results of any stage of latent print analysis (e.g., feature selection, utility 

assessment, discrepancy interpretation) after seeing a known exemplar should be viewed with 

caution. Such modifications should be specifically documented as having occurred after 

comparison has begun. (Recommendation 3.2) 

Procedures should be implemented to protect examiners from exposure to extraneous 

(domain-irrelevant) information in a case. (Recommendation 3.3) 

Several steps in the latent print analysis process require a determination of latent print utility or 

sufficiency. The examiner must determine whether the print has enough clarity and quantity of 

information for some specified purpose. This happens both early in the process (e.g., 

determinations of whether the latent is suitable for analysis or suitable for an automated 

fingerprint identification system search) and later in the process (e.g., determinations of 

sufficient information to compare the latent and exemplar). Forensic service providers can 

enhance the transparency of their analyses and conclusions by promulgating clear guidelines that 
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assist examiners in making determinations of utility.604 Therefore, the Working Group 

recommends:

Each agency or forensic service provider should define “suitable” or “sufficient” in its 

standard operations procedures. These guidelines should be as explicit as possible about what 

is expected for sufficiency determinations at different stages of the latent print examination 

process. (Recommendation 3.4) 

Information that could be incorporated in an agency’s guidelines includes, for example, number 

of minutiae and visibility of ridge flow, pores, ridge edges, and details of incipient ridges, 

creases, and scars.605 For a more detailed discussion of suitability, see Chapter 3, section 3.4. 

Modern investigations often compare latent prints to exemplars from automated fingerprint 

identification system (AFIS) searches. When looking in a large database for those prints that bear 

the greatest similarity to the latent print in question, these programs could select a print from a 

non-source that is far more similar to the latent print than examiners are accustomed to seeing 

from non-matching sources. An examiner whose idea of the necessary amount of information for 

a match comes from a non-database world may not be taking into account the possibility of 

incidental similarity that a large database carries with it. Special care may be warranted in 

interpreting the evidence in such cases. Thus, the Working Group recommends: 

When comparing latent prints to exemplars generated through AFIS searches, examiners 

must recognize the possibility and dangers of incidental similarity. Adjustments such as a 

higher decision threshold, stricter tolerances for differences in appearance, and explicit 

feature weighting need to be considered. Modified quality assurance practices for this 

scenario also should be considered. (Recommendation 3.6) 

10.2 Reporting and Testifying

The forensic part of forensic science distinguishes it from other scientific disciplines. Outside the 

forensic arena, scientists must report their results, but they rarely do so to inform criminal 

investigators, prosecutors, defense counsel, and courts. The needs of these lay consumers of 

forensic science evidence lead to two recommendations. First: 

The report of the examination should ensure that the findings and their limitations are 

intelligible to non-experts. (Recommendation 5.1) 

Second, to maximize the likelihood that the evidence will be used properly, fully, and fairly at 

trial, the report of the results of an examination should: 

 

604 This refers to guidelines for deciding whether a print warrants further assessment and not to guidelines for source 

attribution. Thus, a rule that specifies a minimum number of minutiae for sufficiency might be reasonable because it 

creates a process that is consistent throughout the forensic service provider and transparent to others. Given current 

information, however, a similar rule would not be appropriate for ultimate decision making. 605 The guidelines for determining whether a latent print is suitable for comparison are necessarily different than the 

guidelines for comparing a pair of prints. The Working Group takes no position on whether agencies should couch 

guidelines as recommendations or as requirements.
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a. Identify the latent print examiner(s); 

b. Describe the items submitted to the examiner(s); 

c. List the procedures used by the examiner to develop, visualize, or enhance the friction 

ridge impressions; 

d. List all comparisons conducted; 

e. State all conclusions with the method used to reach them; 

f. Note any important limitations to the conclusions; 

g. Indicate whether a verification was made and whether there was any conflict of 

opinion among examiners prior to the reported conclusions; 

h. Note (or refer to external documentation of) any information about the case that the 

examiner(s) received; 

i. Note the existence of additional documentation; and 

j. Define important technical terms, either explicitly or by reference to an authoritative, 

readily available source. (Recommendation 5.2)

Latent print examiners do more than analyze impressions and prepare written records of their 

work. They testify as expert witnesses who have more latitude than ordinary fact witnesses to 

provide opinions and guidance to jurors. As expert witnesses and as forensic science 

professionals, they have an obligation to their profession and to the court to maintain 

“objectivity, staying within the bounds or limits of what the science can provide, maintaining 

confidentiality, complying [with] legal demands such as disclosure, and being truthful.”606 To 

help maintain this objectivity and “to promote the understanding of examinations and 

findings,”607 the Working Group recommends: 

Forensic service providers should adopt codes of ethics that require testifying in a 

nonpartisan manner; answering questions from both the prosecution and the defense directly, 

accurately, and fully; and providing appropriate scientific information before, during, and 

after trial. (Recommendation 6.2) 

The importance of “staying within the bounds or limits of what the science can provide” and 

providing appropriate scientific information means that, as previously noted in section 10.1, 

“latent print examiners should not report or testify, directly or by implication, to a source 

attribution to the exclusion of all others in the world” (see Recommendation 3.7). 

These goals are most likely to be realized when the expert confers with the lawyer prior to direct 

examination. At a pretrial meeting, the expert can make clear the nature and limits of the 

testimony that the evidentiary material warrants and can work with the lawyer to present this 

information fully, fairly, and clearly. 

The trial preparation process should address the presentation of technical information in lay 

terms, the organization of the direct examination, possible cross-examination, and the 

possible use of visual aids. (Recommendation 6.1) 

 

606 Budowle, B., M. Bottrell, S. Bunch, et al. “A Perspective on Errors, Bias, and Interpretation in the Forensic 

Sciences and Direction for Continuing Advancement.” Journal of Forensic Sciences, 54 (July 2009): 803. 607 Scientific Working Group on Friction Ridge Analysis, Study and Technology. A Model Policy for Friction Ridge 

Examiner Professional Conduct. Version 1.0. Scientific Working Group on Friction Ridge Analysis, Study and 

Technology, December 2008.
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Because absolute certainty is unattainable in science, the witness must be prepared to 

acknowledge and discuss the possibility that an opinion is not correct. Therefore: 

A testifying expert should be familiar with the literature related to error rates. A testifying 

expert should be prepared to describe the steps taken in the examination process to reduce the 

risk of observational and judgmental error. The expert should not state that errors are 

inherently impossible or that a method inherently has a zero error rate. (Recommendation 

6.3) 

Finally, forensic service providers should maintain quality assurance mechanisms for reporting 

and testifying.

 

An agency that employs latent print examiners should establish requirements and guidelines 

for reporting, documentation, and testimony. The agency should review a sample of every 

examiner’s case reports, documentation, and testimony and affidavits at least annually to 

verify compliance with these requirements and guidelines. (Recommendation 6.4) 

10.3 Managing the Process

Latent print examinations do not occur in isolation. Supervision of the staff members and 

management of the facilities are essential to risk reduction and quality assurance and control. 

Effective management requires good information about the incidence and sources of errors. 

Making this information available requires a culture in which both management and staff 

understand that openness about errors is not necessarily a path to punitive sanctions but rather is 

part of an effective system to detect deviations from desired practices and incorrect judgments in 

latent print casework. To achieve such a system, the Working Group recommends: 

Management should foster a culture in which it is understood that some human error is 

inevitable and that openness about errors leads to improvements in practice. 

(Recommendation 9.1) 

Management should employ a system to identify and track errors and their causes. 

(Recommendation 9.2) 

Management should establish policies and procedures for case review and conflict resolution, 

corrective action, and preventive measures. (Recommendation 9.4) 

Furthermore, adherence to appropriate standards is vital to achieving high levels of performance. 

As a result:

All forensic service providers should be accredited by a recognized accrediting body. 

(Recommendation 9.3) 

The latent print community should develop and implement a comprehensive testing program 

that includes competency testing, certification testing, and proficiency testing. 

(Recommendation 9.5)
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Forensic service providers should require personnel to become certified through an 

accredited program. Certifying bodies should review current certification tests with the aid of 

professionals in test design and psychometrics. (Recommendation 8.7 in part) 

Finally, to ensure that latent print examiners maintain their physical capacity to perform at high 

levels of accuracy:

Forensic service providers should institute medical surveillance for examiners with respect to 

activities specific to friction ridge examination. Corrective measures should be taken when 

appropriate and recorded. The program should include a baseline visual examination 

followed by annual vision testing to detect vision deficiencies that may affect interpretation 

of the evidence. (Recommendation 7.2 in part) 

10.4 Improving Training and Education

The need to train and educate examiners on existing procedures and equipment and on emerging 

technologies is a recurring theme in this report. The Working Group’s recommendations involve 

university education, on-the-job training and mentoring, and continuing education. Specifically, 

the Working Group recommends: 

Forensic service providers should require personnel to participate in continuing education. 

(Recommendation 8.7 in part)

The latent print examiner community should expand the training of examiners in elementary 

probability theory to enable examiners to properly utilize the output of probabilistic models. 

(Recommendation 4.3) 

The federal government should consider funding research to determine what educational and 

cognitive abilities should be prerequisites for training a latent print examiner. Forensic 

service providers should have systematic training programs that include these abilities as well 

as education in the scientific method, reading and understanding relevant scientific literature, 

communication skills, and methods for logically developing conclusions. (Recommendation 

8.1) 

Agencies should develop formal mentoring programs that define the responsibilities of the 

mentor, trainee, and supervisor. (Recommendation 8.3) 

Certifying bodies should ensure that examiners have been trained to competency. Laboratory 

accrediting bodies should evaluate the effectiveness of an agency’s training program. 

(Recommendation 8.8) 

Because statistical information plays a fundamental role in weighting latent print feature 

evidence, training should include the best available empirical information and should educate 

examiners about probabilistic reasoning in using that information. (Recommendation 3.5)
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The federal government should establish an expert group to develop a latent print educational 

textbook, practical exercises, and assessment tests (print and online) in consultation with 

professional organizations, senior latent print examiners, researchers with content 

knowledge, experienced trainers, and professionals experienced in curriculum development. 

(Recommendation 8.4) 

The federal government should support a clearinghouse of materials from existing training 

programs as well as publications on latent print identification. (Recommendation 8.6) 

Training materials should include topics beyond the technical aspects of friction ridge 

analysis, such as: 

a. Documentation of work and case notes and written and oral communication; 

b. Professional ethics; 

c. Human factors issues such as fatigue, bias, cognitive influences, perceptual 

influences, and error; 

d. Research methods; and

e. Legal and ethical aspects of expert testimony. (Recommendation 8.5) 

The federal government should develop a forensic latent print examiner scholarship 

program to: 

a. Fund the post-hire training program and, upon successful completion, provide tuition 

reimbursement, loan forgiveness, or other financial assistance to degreed latent print 

examiner trainees working in state, local, or private (not-for-profit) forensic 

laboratories; and

b. Reimburse the employer for a percentage of the salaries during the training period. 

(Recommendation 8.2) 

10.5 Providing Facilities and Equipment

Latent print examinations take place in a physical environment with hardware and software that 

can facilitate the work of the examiners. To achieve the best results in examinations, the 

Working Group recommends: 

A structured approach that involves users throughout the entire design and implementation 

process should be followed when designing technology systems and the physical work 

environment. In addition, forensic service providers should perform usability testing to 

optimize user performance and user satisfaction before deployment. (Recommendation 7.1) 

10.6 Supporting Research Efforts 

An increasing number of research projects are underway, but additional research should be 

undertaken in many areas. For example, the Working Group encountered many questions about 

the existing interpretive process, possible enhancements to it, and other significant matters that 

presently lack definitive answers. There is a critical need for a focused program of research into 

the interpretive process that is at the heart of ACE-V. For example, only a handful of studies 

have assessed variation in the feature selection process. Generally, the findings have shown wide 

variation among examiners during the task of feature selection. Developing methods to reduce 
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204 

the variation of the print features selected for comparisons and the development of tools and 

technologies to assist in the identification of the most reliable features would both be useful. 

While these tools are likely to be especially important for complex comparisons, they may have 

broader benefits. Standardized methods for feature selection should result in less variation in the 

features that are selected and compared, which in turn should lead to more consistency in the 

decisions reported. However, even if decisions were more consistent, they would not necessarily 

be more accurate. Even the best interpreters of prints should be willing to compare their own 

methods to a standard protocol to decide which practice is best. 

Furthermore, the link between variations in feature selection and the examiner’s ultimate 

decision is not well understood. Emerging research suggests that there is a relationship, but the 

effect may be competing with other major interpretative steps, such as interpreting discrepancy, 

feature weighting, and thresholds for reaching identification decisions. A better understanding of 

the link between feature selection and the ultimate decision would permit best practices to be 

formulated. This knowledge would also allow technology systems to select the most reliable and 

useful features on which to base decisions later in the ACE-V process. 

The Working Group found no research that explicitly addresses utility or sufficiency in the 

context of latent print analysis. This is unsurprising, for a critical piece for any such research—

the definition and validation of a metric for assessing utility—is missing. Research has been 

carried out related to the examiner decision process that implicitly involves judgments of utility 

and sufficiency, but these studies tend to focus only on the accuracy or repeatability of the 

ultimate decision. For example, the Noblis-FBI study described in Chapter 2 treats the ACE-V 

process as a “black box.” The experimenters provide the input and measure the output in various 

ways. This kind of research provides valuable information on how examiners perform relative to 

“ground truth” (accuracy) and how their results compare to one another (reliability). Opening the 

box to study the process of judgment in every phase of ACE-V would provide the empirical 

foundation from which to develop best practices for each part of the process. As a result, the 

Working Group recommends: 

The federal government should support a research program that aims to: 

a. Develop measures and metrics relevant to the analysis of latent prints; 

b. Use such metrics to assess the reproducibility, reliability, and validity of various 

interpretive stages of latent print analysis; and

c. Identify key factors related to variations in performance of latent print examiners 

during the interpretation process. (Recommendation 3.9) 

Practitioners recognize that assigning weights to latent print features and their configurations is a 

fundamental decision-making or interpretive step, either as an output of the Analysis phase or as 

part of the Evaluation phase. Pioneers such as Locard indicated that fingerprint features should 

be assessed as a function of their relative rarity (allowing also for a proper consideration of their 

clarity).608

 

608 Locard, E. “La Preuve Judiciaire par les Empreintes Digitales.” Archives d’Anthropologie Criminelle, de 

Médecine Légale et de Psychologie Normale et Pathologique, 29 (1914): 321 – 48.

 Currently, however, the weighting of individual features is mainly based upon 

subjective, experience-based judgments of the probability associated with their occurrence. In 

fact, in one study, latent print examiners did not provide consistent rankings of how frequently 
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fingerprint features occur.609 No clear consensus exists among practitioners as to the 

reproducibility and perceived contribution of Level 3 Detail features appearing in both latent and 

the exemplar print.610 Carefully collected data should be used to provide more accurate 

assessments that can inform the weighting of features in the interpretive process. 

This statistical data also could be incorporated into formal probabilistic models of various kinds 

(see Chapter 4). In addition to providing both a firmer foundation for and opportunities to 

improve the judgments of examiners, such modeling can supply objective probabilities that 

would be useful to judges or juries (Chapter 6). Before that can happen, however, large datasets 

will be needed to validate the emerging models more fully. The Working Group therefore 

recommends: 

To facilitate the validation of probabilistic models and other statistical research, the federal 

government should create large, anonymous databases of exemplars and latent prints. 

(Recommendation 4.2) 

Visual acuity is vital to the examination process, and section 10.3 included a recommendation for 

medical monitoring. To permit the most effective monitoring, the Working Group also 

recommends:

The federal government should support research to determine the most appropriate tests of 

visual function for friction ridge examiners. (Recommendation 7.2 in part) 

As discussed in Chapter 4 and section 10.4, AFIS technology has proven to be of great value in 

efficiently locating candidate exemplars for examiners to compare to a questioned print. The 

design of these systems could be improved in several respects. 

The federal government should support research programs to improve automated fingerprint 

identification systems. Such programs could address the following issues: 

a. Expanding the algorithms used to match prints to account for the fact that the 

diagnostic value of minutiae depends on the region in which they are located; 

b. Making fingerprint and palm print databases interoperable among local, state, and 

federal automated identification systems; and

c. Increasing compatibility between automated identification systems and other latent 

print software tools, including digital enhancement programs, probability calculation 

programs, and automated quality assessment programs. (Recommendation 4.1)

The reference above to automated quality assessment programs relates to Recommendation 3.9 

for research into the interpretative process. In the experience of the Working Group, the initial 

quality assessment of the latent print is often the weak link in the analytical process, as 

examiners are susceptible to making one of two types of errors. In the first type of error, the 

examiner prematurely discards a print that should be deemed suitable for further analysis and 

comparison, possibly resulting in a missed identification. In the second type of error, the 

 

609 Osterburg, J. “An Inquiry into the Nature of Proof. The Identity of Fingerprints.” Journal of Forensic Sciences, 9, 

no. 4 (1964): 413 – 27.

610 Anthonioz, A., N. Egli, C. Champod, et al. “Level 3 Details and Their Role in Fingerprint Identification: A 

Survey Among Practitioners.” Journal of Forensic Identification, 58, no. 5 (2008): 562 – 89.
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206 

examiner continues to evaluate a latent print that ought to be deemed unsuitable for further 

processing. This outcome results in wasted time and might even contribute to an erroneous 

identification. Although efforts to develop automated quality assessment programs have had 

limited success, a concerted effort to automate the quality assessment step, at least partially, is 

worthwhile. In addition to Recommendation 3.9(a), the Working Group proposes: 

The federal government should continue funding research into automation of the initial 

quality assessment step in latent print analysis. (Recommendation 4.4) 

Latent print analysis provides perhaps the single most common type of forensic science 

evidence. It is critical to the successful operation of the criminal justice system. The 

recommendations listed above do not exhaust this report’s suggestions for improving the 

understanding and management of human factors issues in this vital work. Related suggestions, 

explanations, and ideas are found in each chapter. Translating these ideas into practice will make 

the analysis and presentation of a crucial source of information even more effective and reliable.
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Chapter 10: Summary of Recommendations 

207 

Appendix 10-A: List of Recommendations

Recommendation 3.1: A report and contemporaneous supporting notes or materials should 

document the examination to make the interpretive process as transparent as possible. Although 

the degree of detail may vary depending on the perceived complexity of the comparison, 

documentation should, at a minimum, be sufficient to permit another examiner to assess the 

accuracy and validity of the initial examiner’s assessment of the evidence. 

Recommendation 3.2: Modifications to the results of any stage of latent print analysis (e.g., 

feature selection, utility assessment, discrepancy interpretation) after seeing a known exemplar 

should be viewed with caution. Such modifications should be specifically documented as having 

occurred after comparison had begun. 

Recommendation 3.3: Procedures should be implemented to protect examiners from exposure to 

extraneous (domain-irrelevant) information in a case. 

Recommendation 3.4: Each agency or forensic service provider should define “suitable” or 

“sufficient” in its standard operations procedures. These guidelines should be as explicit as 

possible about what is expected for sufficiency determinations at different stages of the latent 

print examination process. 

Recommendation 3.5: Because statistical information plays a fundamental role in weighting 

latent print feature evidence, training should include the best available empirical information and 

should educate examiners about probabilistic reasoning in using that information. 

Recommendation 3.6: When comparing latent prints to exemplars generated through AFIS 

searches, examiners must recognize the possibility and dangers of incidental similarity. 

Adjustments such as a higher decision threshold, stricter tolerances for differences in appearance, 

and explicit feature weighting need to be considered. Modifying quality assurance practices for 

this scenario also should be considered. 

Recommendation 3.7: Because empirical evidence and statistical reasoning do not support a 

source attribution to the exclusion of all other individuals in the world, latent print examiners 

should not report or testify, directly or by implication, to a source attribution to the exclusion of 

all others in the world. 

Recommendation 3.8: The friction ridge examiner community and other experts should 

determine under what circumstances a qualified rather than an absolute conclusion is warranted. 

Recommendation 3.9: The federal government should support a research program that aims to: 

a. Develop measures and metrics relevant to the analysis of latent prints; 

b. Use such metrics to assess the reproducibility, reliability, and validity of various 

interpretive stages of latent print analysis; and

c. Identify key factors related to variations in performance of latent print examiners during 

the interpretation process.
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Chapter 10: Summary of Recommendations 

208 

Recommendation 4.1: The federal government should support research programs to improve 

automated fingerprint identification systems. Such programs could address the following issues: 

a. Expanding the algorithms used to match prints to account for the fact that the diagnostic 

value of minutiae depends on the region in which they are located; 

b. Making fingerprint and palm print databases interoperable among local, state, and federal 

automated identification systems; and

c. Increasing compatibility between automated identification systems and other latent print 

software tools, including digital enhancement programs, probability calculation 

programs, and automated quality assessment programs. 

Recommendation 4.2: To facilitate the validation of probabilistic models and other statistical 

research, the federal government should create large, anonymous databases of exemplars and 

latent prints. 

Recommendation 4.3: The latent print examiner community should expand the training of 

examiners in elementary probability theory to enable examiners to properly utilize the output of 

probabilistic models. 

Recommendation 4.4: The federal government should continue funding research into automation 

of the initial quality assessment step in latent print analysis.

Recommendation 5.1: The report of the examination should ensure that the findings and their 

limitations are intelligible to non-experts.

Recommendation 5.2: A report should: 

a. Identify the latent print examiner(s); 

b. Describe the items submitted to the examiner(s); 

c. List the procedures used by the examiner to develop, visualize, or enhance the friction 

ridge impressions; 

d. List all comparisons conducted; 

e. State all conclusions with the method used to reach them; 

f. Note any important limitations to the conclusions; 

g. Indicate whether a verification was made and whether there was any conflict of opinion 

among examiners prior to the reported conclusions; 

h. Note (or refer to external documentation of) any information about the case that the 

examiner(s) received; 

i. Note the existence of additional documentation; and 

j. Define important technical terms, either explicitly or by reference to an authoritative, 

readily available source.

Recommendation 6.1: The trial preparation process should address the presentation of technical 

information in lay terms, the organization of the direct examination, possible cross-examination, 

and the possible use of visual aids. 

Recommendation 6.2: Forensic service providers should adopt codes of ethics that require 

testifying in a nonpartisan manner; answering questions from both the prosecution and the 
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Chapter 10: Summary of Recommendations 

209 

defense directly, accurately, and fully; and providing appropriate scientific information before, 

during, and after trial. 

Recommendation 6.3: A testifying expert should be familiar with the literature related to error 

rates. A testifying expert should be prepared to describe the steps taken in the examination 

process to reduce the risk of observational and judgmental error. The expert should not state that 

errors are inherently impossible or that a method inherently has a zero error rate. 

Recommendation 6.4: An agency that employs latent print examiners should establish 

requirements and guidelines for reporting, documentation, and testimony. The agency should 

review a sample of every examiner’s case reports, documentation, and testimony and affidavits 

at least annually to verify compliance with these requirements and guidelines. 

Recommendation 7.1: A structured approach that involves users throughout the entire design and 

implementation process should be followed when designing technology systems and the physical 

work environment. In addition, forensic service providers should perform usability testing to 

optimize user performance and user satisfaction before deployment.

Recommendation 7.2: Forensic service providers should institute medical surveillance for 

examiners with respect to activities specific to friction ridge examination. Corrective measures 

should be taken when appropriate and recorded. The program should include a baseline visual 

examination followed by annual vision testing to detect vision deficiencies that may affect 

interpretation of the evidence. The federal government should support research to determine the 

most appropriate tests of visual function for friction ridge examiners. 

Recommendation 8.1: The federal government should consider funding research to determine 

what educational and cognitive abilities should be prerequisites for training a latent print 

examiner. Forensic service providers should have systematic training programs that include these 

abilities as well as education in the scientific method, reading and understanding relevant 

scientific literature, communication skills, and methods for logically developing conclusions. 

Recommendation 8.2: The federal government should develop a forensic latent print examiner 

scholarship program to: 

a. Fund the post-hire training program and, upon successful completion, provide tuition 

reimbursement, loan forgiveness, or other financial assistance to degreed latent print 

examiner trainees working in state, local, or private (not-for-profit) forensic laboratories; 

and

b. Reimburse the employer for a percentage of the salaries during the training period. 

Recommendation 8.3: Agencies should establish formal mentoring programs that define the 

responsibilities of the mentor, trainee, and supervisor. 

Recommendation 8.4: The federal government should establish an expert group to develop a 

latent print educational textbook, practical exercises, and assessment tests (print and online) in 

consultation with professional organizations, senior latent print examiners, researchers with 

content knowledge, experienced trainers, and professionals experienced in curriculum 

development. 
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Chapter 10: Summary of Recommendations 

210 

Recommendation 8.5: Training materials should include topics beyond the technical aspects of 

friction ridge analysis, such as: 

a. Documentation of work and case notes and written and oral communication; 

b. Professional ethics; 

c. Human factors issues such as fatigue, bias, cognitive influences, perceptual influences, 

and error; 

d. Research methods; and

e. Legal and ethical aspects of expert testimony.

Recommendation 8.6: The federal government should support a clearinghouse of materials from 

existing training programs as well as publications on latent print identification.

Recommendation 8.7: Forensic service providers should require personnel to participate in 

continuing education and to become certified through an accredited program. Certifying bodies 

should review current certification tests with the aid of professionals in test design and 

psychometrics.

Recommendation 8.8: Certifying bodies should ensure that examiners have been trained to 

competency. Laboratory accrediting bodies should evaluate the effectiveness of an agency’s 

training program. 

Recommendation 9.1: Management should foster a culture in which it is understood that some

human error is inevitable and that openness about errors leads to improvements in practice. 

Recommendation 9.2: Management should employ a system to identify and track errors and their 

causes.

Recommendation 9.3: All forensic service providers should be accredited by a recognized 

accrediting body.

Recommendation 9.4: Management should establish policies and procedures for case review and 

conflict resolution, corrective action, and preventive measures. 

Recommendation 9.5: The latent print community should develop and implement a 

comprehensive testing program that includes competency testing, certification testing, and 

proficiency testing. 
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The Report of the Expert Working Group on Human Factors in Latent Print Analysis

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