Standard for Examining 

Friction Ridge Impressions

Friction Ridge Subcommittee

Physics/Pattern Scientific Area Committee

Organization of Scientific Area Committees (OSAC) for Forensic Science
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Standard for Examining Friction Ridge Impressions

OSAC Proposed Standard

Standard for Examining Friction 

Ridge Impressions

Prepared by

Friction Ridge Subcommittee

Organization for Scientific Area Committees (OSAC) for Forensic Science

Version: 1.0

September 2020

Disclaimer:

This document has been developed by the Friction Ridge Subcommittee of the Organization of 

Scientific Area Committees (OSAC) for Forensic Science through a consensus process and 

proposed for further development through a Standard Developing Organization (SDO). This 

document is being made available so that the forensic science community and interested parties

can consider the recommendations of the OSAC pertaining to applicable forensic science 

practices. The document was developed with input from experts in a broad array of forensic 

science disciplines as well as scientific research, measurement science, statistics, law, and policy.

This document has not been published by a SDO. Its contents are subject to change during the 

standards development process. All stakeholder groups or individuals are strongly encouraged to 

submit comments on this proposed document during the open comment period administered by 

the Academy Standards Board (ASB). 
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Standard for Examining Friction Ridge Impressions

Table of Contents

1. Introduction ..................................................................................................................... 1

2. Scope ................................................................................................................................. 1

3. Terms and Definitions..................................................................................................... 1

4. General Requirements .................................................................................................... 3

4.1. Analysis....................................................................................................................... 3

4.2. Comparison ................................................................................................................. 5

4.3. Evaluation.................................................................................................................... 6

5. Appendix A: Change Log................................................................................................ 6
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Standard for Examining Friction Ridge Impressions

1. Introduction

1.1. This document has been developed with the objective of improving the quality and 

consistency of friction ridge examination practices.

1.2. The examination of friction ridge impressions is conducted in accordance with a 

methodology consisting of Analysis, Comparison, and Evaluation. Analysis is the 

interpretation of observed data in a friction ridge impression in order to categorize its 

utility. Comparison is the search for and detection of similarities and differences in the 

observed data between two potentially corresponding friction ridge impressions. 

Evaluation is the weighting of the aggregate strength of the observed similarities and 

differences between the observed data in the two friction ridge impressions in order to 

formulate a source conclusion.

1.3. In this document, the following verbal forms are used: “shall” indicates a requirement, 

“should” indicates a recommendation; “may” indicates permission; and “can” indicates a 

possibility or capability. 

2. Scope

2.1. This document specifies the minimum requirements for conducting friction ridge 

examinations. It includes the overarching examination framework as well as specific 

requirements for each component of any examination methodology. This document 

includes minimum requirements for conducting, documenting, and justifying 

examinations based on clearly demonstrable and articulable criteria. 

2.2. This document does not address specific requirements for quality assurance / quality 

control of the examination methodology.

3. Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

3.1. Analysis (phase of the Examination methodology): The interpretation of observed data 

in a friction ridge impression in order to categorize its utility. 

3.2. Comparison (phase of the Examination methodology): The search for and detection of 

similarities and differences in observed data between two potentially corresponding 

friction ridge impressions. 

3.3. Complexity (of a Comparison): A characteristic of a comparison in which the attributes 

of one or both impressions may require additional consideration and quality control 

measures as it relates to the evaluation of a source conclusion. Comparisons can be 

designated as high complexity, low complexity, or non-complex.
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Standard for Examining Friction Ridge Impressions

3.4. Complexity (of an Impression): A characteristic of an impression whose attributes may 

require additional consideration and quality control measures. Impressions can be 

designated as high complexity, low complexity, or non-complex.

3.5. Evaluation (phase of the Examination methodology): The weighting of the aggregate 

strength of the observed similarities and differences between the observed data in the 

two friction ridge impressions in order to formulate a source conclusion.

3.6. Examination: The act or process of observing, searching, detecting, recording, 

prioritizing, collecting, analyzing, measuring, comparing, and/or interpreting.

3.7. Exemplar Impression: An impression to which a questioned impression is compared; it 

can include impressions from an unknown source or a known source.

3.8. Forensic Service Provider (FSP): A forensic science entity or forensic science 

practitioner providing forensic science services.

3.9. Friction Ridge Detail/Features: The combination of ridge flow, ridge characteristics, 

and ridge structure of friction ridge skin, as observed and reproduced in an impression. 

A large subset of the observed data used to compare and interpret similarity or 

dissimilarity between two impressions.

3.10. High Quality Impression: An impression with observed data that are unambiguous and 

self-evident due to high clarity and quantity.

3.11. Interpretation: Explanations for the observations, data, and calculations.

3.12. Observed Data: Any demonstrable information observed within an impression that an 

examiner relies upon to reach a decision, conclusion, or opinion. This has historically 

been expressed as “features” or “minutiae,” but the use of the broader term “observed 

data” is inclusive of other types of data that may be considered beyond minutiae, such 

as quality, scars, creases, edge shapes, pore structure, and other friction ridge features.

3.13. Questioned Impression: An impression used for comparison against an exemplar 

impression; it can include impressions from an unknown source or a known source.

3.14. Suitability for Comparison Decision (Suitability for Source Conclusions): A decision 

made by an examiner in accordance with FSP policy and/or procedure, that a friction 

ridge impression contains sufficient observed data to be utilized for comparison and a 

Source Conclusion can potentially be reached. This designation is often referred to as 

“suitable for comparison” or “of value for comparison”.

3.15. Utility: The usefulness of an impression for a further step in the examination process, 

such as comparison or Automated Biometric Identification System entry.
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Standard for Examining Friction Ridge Impressions

4. General Requirements

4.1. Analysis

4.1.1. The FSP shall define the observed data examiners may use during the 

examination of friction ridge impressions. The observed data that the FSP may 

consider include:

4.1.1.1. Size and shape of the impression: the (surface area) and the outline of the 

impression border

4.1.1.2. Classification patterns: the presence, size, and shape of defined 

classifiable patterns present in the friction ridge skin (e.g. arch, loop, 

whorl).

4.1.1.3. Cores and deltas: the existence, number, position, and shape of the cores 

and deltas.

4.1.1.4. Ridge flows: the overall ridge flow that may lack a classifiable pattern but 

facilitate the search.

4.1.1.5. Flexion crease: the existence, position, and path of flexion creases.

4.1.1.6. Secondary creases or wrinkles: the existence, position, path, and density of 

secondary creases or wrinkles.

4.1.1.7. Scars: the existence, position, and path of scars.

4.1.1.8. Occasional features: the existence, position, and path of occasional 

features (e.g. warts or healing skin).

4.1.1.9. Ridge paths: the location, direction, length, width, and curvature of the 

path of a ridge.

4.1.1.10. Minutiae: the location, type, and direction of minutiae.

4.1.1.11. Ridge morphology: the edge shapes or texture of a ridge.

4.1.1.12. Incipient ridges: the location, direction, length, width, morphology, and 

density of incipient ridges.

4.1.1.13. Flexion crease morphology: the edge shapes or texture of a flexion crease.

4.1.1.14. Scar morphology: the edge shapes or texture of a scar.
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Standard for Examining Friction Ridge Impressions

4.1.1.15. Occasional feature morphology: the edge shapes or texture of an 

occasional feature.

4.1.1.16. Spatial relationships: the ridge counts, distances, directions, and angles 

between features.

4.1.2. The FSP shall have a written procedure for routinely monitoring examiners’ 

ability to interpret observed data. This monitoring shall be planned and 

documented.

4.1.3. The FSP shall define the utility decisions that may be used in casework. This is 

an operational decision, not a scientific one, and FSP policies shall include a 

statement of this effect. At a minimum, the utility decisions shall include 

suitability for proceeding to a comparison. If applicable, it shall also include 

suitability for database search.

NOTE: While there is no scientific basis for selecting a particular 

threshold to establish the utility of an impression, an agency may choose 

to set a threshold for operational reasons, such as available resources. In 

theory, any friction ridge impression could be compared, but many are so 

fragmentary that a meaningful conclusion could not be reached or 

supported, thus it would be inefficient and ineffective to do so. Similarly, 

an agency may make an operational decision not to proceed with 

comparison of some impressions because of a higher perceived risk of 

error.

4.1.4. The FSP shall have a written procedure for documenting the anatomical region(s) 

and orientation(s) assigned.

4.1.5. The FSP shall have a written procedure for routinely monitoring examiners’ 

assignments of anatomical region and orientation. This monitoring shall be 

planned and documented.

4.1.6. The FSP shall define the criteria for utility decisions. At a minimum, the criteria 

shall include the observed data necessary to decide the utility of the impression. 

4.1.7. The FSP shall have a written procedure for documenting which impressions will 

proceed to a further step (commonly known as “of value” or “suitable”) and, if 

applicable, database search. This procedure shall include a method for indicating 

which impressions will not proceed to a further step (commonly known as “no 

value” or “not suitable” impressions). 

NOTE 1: This may be achieved by a blanket policy stating that any 

unlabeled impressions will not proceed to a further step. 
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Standard for Examining Friction Ridge Impressions

NOTE 2: “Unlabeled” means an impression that has not been marked or 

named to “claim” it for further use.

4.1.8. The FSP shall have a written procedure for documenting which impressions have 

been designated as “complex” and may have a procedure for documenting which 

impressions have been designated as “high quality”.

4.1.9. The FSP shall have a written procedure for documenting the information that 

supports the utility decision. The procedure shall address:

4.1.9.1. Method of documentation (e.g. marking hard-copies or using software 

programs).

NOTE: For automated search processes, the auto-encoded features may be 

retained as documentation.

4.1.9.2. Documentation of the support for the utility decision. This shall include, 

at a minimum, the observed data relied upon. Documentation of the 

observed data in the unknown friction ridge impression shall take place 

prior to proceeding to the next step.

4.1.9.3. Criteria for increasing or decreasing the level of documentation of the 

information (generally based on the complexity of the impression or the 

complexity of the case)

4.1.10. The FSP shall have a written procedure for routinely monitoring examiners’ 

utility decisions and their documentation of the observed data used to support the 

utility decision. This monitoring shall be planned and documented.

4.2. Comparison

4.2.1. The FSP shall have a written procedure for specifying and documenting which 

questioned friction ridge impressions and individuals were compared.

4.2.2. The FSP shall have a written procedure for documenting relevant information 

regarding the known friction ridge impression (e.g. name, identifier, date 

recorded).

4.2.3. The FSP shall have a written procedure for documenting exemplar friction ridge 

impressions that are not suitable to complete comparisons.

NOTE 1: Requirements for documentation of corresponding regions are 

specified in section 4.3.4.
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Standard for Examining Friction Ridge Impressions

NOTE 2: The requirements in Section 4.2 do not apply to comparisons made 

during database candidate list screening/comparison.

4.3. Evaluation

4.3.1. The FSP shall define the source conclusions available for use in casework.

4.3.2. The FSP shall define the criteria for each source conclusion. 

4.3.3. The FSP shall require that the source conclusion reached for each comparison be 

recorded.

4.3.4. The FSP shall have a procedure for documenting the observed data that support 

source conclusions. The procedure shall address:

4.3.4.1. Method of documentation (e.g. marking hard-copies or using software 

programs).

4.3.4.2. The observed data used to support the conclusion. 

4.3.4.3. Criteria for increasing or decreasing the documentation of the observed 

data (generally based on the complexity of the comparison or the case).

4.3.4.4. Changes in the interpretation of the observed data in the questioned

friction ridge impression after the initiation of the comparison process.

4.3.5. The FSP shall have a procedure for routinely monitoring examiners’ ability to 

appropriately formulate source conclusions. This monitoring shall be planned and 

documented.

NOTE: In addition to the source conclusions, the procedure should also include 

the monitoring of the examiners’ documentation of observed data.

5. Appendix A: Change Log

Version Date Change

1.0 09/30/2020 Original Issue