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NATIONAL COMMISSION ON 

FORENSIC SCIENCE

Inconsistent Terminology

Type of Work Product: Views Document issued by the Reporting and Testimony 

Subcommittee

Statement of the Issue

It is the view of the National Commission on Forensic Science (NCFS) that the forensic science 

community should endeavor to make terminology more consistent within a particular discipline 

and across disciplines. Adoption of terminology is a fundamental step to clear communication of

scientific testing results and conclusions. Clear and consistent language within, as well as across 

forensic disciplines will improve communication among scientists, law enforcement, lawyers, 

judges and the public. This document summarizes problems that result from the inconsistent use 

of terminology within and across disciplines and suggests a framework for creating standardized 

terminology.

Background

A. Why Should Terminology Be Uniform?

In its simplest terms, “[i]t does little good to gather great data and to carefully interpret it – and 

then fail to effectively share this information with those who need to understand what the data 

means.”1 Similarly, the National Research Council observed that “[i]nconsistency or ambiguity 

in terminology can and does have a profound effect on how the trier of fact in a criminal or civil 

matter perceives and evaluates scientific evidence.”2Inconsistent terminology also prevents other 

forensic experts from meaningfully assessing or relying on an expert’s finding or opinion.

Outside of forensic science, the international Joint Committee for Guidelines in Metrology which

produced the International Vocabulary of Metrology (VIM) framed the importance of clear and 

unambiguous language as follows:

Scientists from different sectors often attach different words to the same concept; 

this makes interdisciplinary conversations very difficult and confusing. There needs 

to be a common language that is clear and unambiguous. The first thing one does 

when learning any new language is to acquire a vocabulary, which will grow in 

time. Anyone learning a new language will know that there are many peculiarities 

 

1

John M. Butler, Forensic DNA Typing III – Advanced Topics: Interpretation, chapter 16 – Laboratory Reports: 

Communicating Results and Conclusions, Elsevier Academic Press 2014.

2 National Research Council Committee on Identifying the Needs of the Forensic Science Community, 

Strengthening Forensic Science in the United States: A Path Forward, p. 21 (2009)[hereinafter NRC Forensic Science 

Report]
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in any language, from words that can have different meanings depending on the 

context, to words that sound the same but are spelled differently and obviously have 

a different meaning. In English the word ‘standard’ has often been cited as an 

example of a word with many meanings. A detailed knowledge of the language is 

required to avoid such words causing mistakes, especially for people who do not 

have English as a first language. Ambiguous terminology also becomes a problem 

for translators and can be a direct barrier to trade.

3

To some degree standardized language is beginning to be incorporated across forensic disciplines.4 

For example, ISO/IEC 17025, a foundational document for accrediting bodies, uses the VIM as a 

normative reference leading to some standardization of terminology in accredited laboratories.

5

However, the VIM is targeted toward analytical laboratories and addresses only measurements. 

Forensic practitioners also communicate about inferences and concepts that extend beyond

measurements

6

and they have the additional challenge of communicating with participants in the

legal system for whom science is not their first language. 

B. Examples of Inconsistent Language

The NRC Forensic Science Report expressed concern about terms such as “match,” “consistent 

with,” “identical,” “similar in all respects tested,” and “cannot be excluded as the source of.” It 

asserted that these terms can have a “profound effect on how the trier of fact in a criminal or civil 

case perceives and evaluates scientific evidence.”7 The American Bar Association’s Resolution 

101C(2) urges judges to regulate the manner in which expert testimony should be presented at trial

and to consider whether “experts used clear and consistent terminology in presenting their 

opinions.”8

This does not necessarily mean that such terminology should never be used, but care must be given 

to choosing the most transparent terms and clearly defining them in report writing and testimony. 

Inconsistent terminology can lead to miscommunication both within and across disciplines. The 

overstatement or exaggeration of the value and/or limitations of the information and confusion as 

to the meaning of terminology by the end users can lead to the word’s misapplication. Below are 

examples of these problems.

1. Inconsistency in Terminology Both Within and Across Disciplines

Inconsistences in terminology across disciplines can create confusion. When the same terminology 

is used differently across disciplines and presented in the courtroom to express findings to a nonscientific audience, the subtleties in its use may be lost on the audience. 

 

3 V J Barwick and E Prichard (Eds), Eurachem Guide: Terminology in Analytical Measurement – Introduction to VIM 

3 (2011). 

4

Id.

5

Id.

6 But see Rene’ Dybkaer, Definitions of “Measurement”, 16 Accreditation & Quality Assurance 479 

(2011)(identifying vagueness in the scope of the term “measurement”).

7 NRC Forensic Science Report, supra note 1, at 21.

8 ABA Resolution 101C(2)
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One example of a term that is used inconsistently in two or three disciplines is the use of the word 

“perimortem.” “When using the term perimortem, medical doctors are referring to the “person” 

(body), whereas the forensic anthropologist is referring to bone.’

9 The Scientific Working Group 

for Anthropology (SWGANTH) has attempted to address this “hard-to-define word within the 

special area of trauma analysis.”10 When defining “perimortem trauma” the organization cautions 

practitioners by saying, “...consideration should be given to: cautious use of the term perimortem, 

since it is used with varied temporal precisions within the forensic community; thus an explanation 

of the term should be provided with clear reasons for a perimortem classification...”11

This use of caution when there is great difficulty in applying a clear and concise meaning to a term 

is one option. However, robust discussion and careful consideration of the language is crucial. 

Clarifying, standardizing or abandoning the use of terminology that is confusing and/or not helpful 

in furthering communication across disciplines should all be carefully considered. 

Another example is terminology used to express the potential association between two objects in

comparative practices. Terms such as “match,” “consistent with,” “excluded,” and “inconclusive” 

are used in various disciplines to describe the relationship between an evidentiary sample, often 

called a “question” sample (Q) and a “known” sample (K). These definitions can express 

dramatically different values in the comparisons depending on the discipline, as well as there being

disagreement within disciplines. 

“Inconclusive” is one of these terms. The Association of Firearm and Tool Mark Examiners have 

defined this word to describe three separate situations:

A. Agreement of all discernible class characteristics and some agreement of 

individual characteristics, but insufficient for an identification. 

B. Agreement of all discernible class characteristics without agreement or 

disagreement of individual characteristics due to an absence, insufficiency, or 

lack of reproducibility. 

C. Agreement of all discernable class characteristics and disagreement of individual 

characteristics, but insufficient for an elimination.12

In DNA typing, “inconclusive” is used in a similar way to mean instances when a practitioner 

cannot clearly include or exclude a known profile from a question sample. Yet in DNA the causes 

for such a statement are varied. The original Q sample yielded no data or limited data due to the 

quality of the sample from degradation, inhibition in the amplification process or a low amount of 

DNA. A second possibility might be that there is too much information from multiple contributors 

(a complex mixture) making the sample too complex to interpret.13

 

9 Ann S. Bunch, National Academy of Sciences “Standardization”: On What Terms?, J. Forensic Sci., July 14, Vol. 59, 

No. 4, dio: 10.1111/1556-4029.12496, available online at: onlinelibrary.wiley.com. (Providing a detailed discussion 

on the multiple definitions, origins and use of these terms in medicine and forensic anthropology).

10 Id.

11 Id., quoting, SWGANTH website (Trauma Analysis section dated 5/27/2011)(the language referenced on the 

SWGANTH website remains the same as January 6, 2015).

12 Association of Firearm & Tool Mark Examiners, Glossary, 6th Edition, version 6.120414 (2013).

13 John M. Butler, Forensic DNA Typing III – Advanced Topics: Interpretation, chapter 16 – Laboratory Reports: 

Communicating Results and Conclusions, Elsevier Academic Press 2014. See also, SWGDAM Guidelines.
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An explanation in reporting “inconclusive” can create some clarification but choosing more 

consistent terminology could avoid the confusion all together. 

One of the problems with the use of similar or identical terms to describe different values in 

different disciplines is the confusion these definitions can cause in the courtroom. If “consistent 

with” or “match” means one thing in one discipline and has a totally different value ascribed to it 

in another, a lawyer, judge or juror is left to try to not only understand the nuance of the particular 

discipline but sort out the confusion in different terminology. In the mind of most jurors words 

like “match” mean that the compared items come from the same source and none other.14

Since the vast majority of criminal cases settle prior to trial, there is great danger in the reader

misunderstanding the message and then misapplying the information when investigating a 

potential suspect, charging an individual with a crime, explaining findings to a victim or the public 

or advising a client about whether to enter into a plea agreement. Each of these scenarios can have 

deleterious results such as an individual not being charged with a crime when they should have 

been, others accused of crimes when they should not be or not properly assessing the strength of a 

prosecution or defense. These scenarios are not highlighted by appellate cases which typically 

address a miscarriage of justice when someone has been wrongfully convicted, but the harm can 

be just as great. Commissioners did not have a specific example of how this manifests itself but 

understand that there are many practitioners who have dedicated hours of time discussing and 

exploring ways to better communicate the meaning of findings such as “inconclusive.”

2. Overstatement or Exaggeration of Meaning and/or Limitations

When terms are not clearly defined, they might not convey their intended meaning. In Williamson 

v. Reynolds, for example, an expert testified that hair samples were “consistent microscopically.”15

The question becomes, “what does this term mean?” Does it mean the same as “consistent with?” 

Without further explanation, which was not provided, the evidence may have little probative value 

but the jury may not appreciate this fact.16 In fact, in Williamson, the problem was exacerbated 

 

14 Statistics are used in DNA typing to express the value of a comparison. The use of statistics can be a powerful 

tool to express the value of the comparison but statistical modeling will also have to address the challenges that 

come with the use of different statistical models answering different questions and the challenges in expressing 

these nuances to a non-scientific audience.

15 Williamson v. Reynolds, 904 F. Supp. 1529, 1558 (E.D. Okl. 1995), rev’d sub nom. on this ground, Williamson v. 

Ward, 110 F.3d 1508, 1523 (10th Cir. 1997).

16 Some believe that microscopic hair analysis should not be used as an example of inconsistent terminology 

because this particular field has been the subject of great criticism; the problems extend beyond inconsistent 

terminology and instead highlight the problems involved in testifying outside the limits of science. However, this 

example provides a concrete real life example of what can and does occur when practitioners try to explain poorly 

defined terminology. The community as a whole has made and continues to make attempts to respond in these 

cases. For example, in April of 2013 ASCLD/LAB Board of Directors sent notice to their membership recommending 

that laboratories consider appropriate action in reviewing cases. http://www.ascld-lab.org/notification-from-theascldlab-board-of-directors-to-interested-parties-concerning-potential-issues-with-hair-comparison-testimony. 

The work that the FBI, the Innocence Project and the National Association of Criminal Defense Lawyers are doing in 

an attempt to rectify damage caused by this analysis also serves as an example of how stakeholders working 

together can improve the system as a whole. In the context of inconsistent terminology, this example highlights a 

challenge present in number of other pattern and impression evidence disciplines that struggle with how to 

express and measure the value of their comparisons. Their intentions and efforts are laudable. This example as 
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because the expert during the trial went on to explain: “In other words, hairs are not an absolute 

identification, but they either came from this individual or there is – could be another individual 

somewhere in the world that would have the same characteristics to their hair.”17 This phrasing 

suggests that very few people in the world would have “consistent” hair - a gross overstatement. 

This example highlights the problem with terminology that overstates the value of the information 

in the context of testimony. When examiners are trying to explain their findings but do not have 

clear and concise terminology upon which to rely, there is a temptation to try to clarify, which can 

lead to redefining the term, sometimes overstating the conclusion and creating even more 

confusion. 

The same lack of clarity in report writing can lead to just as damaging results as it drives the 

decision making process of the reader who could also misunderstand terminology that is not clear 

and consistent. Although it is not certain that concise and properly defined terminology would 

have totally avoided this problem, such enhanced terminology makes it unnecessary for the 

attorney to press an expert for clarification and give the expert a clear and concise definition to 

rely on rather than creating some variation on the fly.

3. Confusion As to Meaning and Misapplication as a Result

This challenge is often tied to the temptation to overstate or re-define a term and therefore, 

exaggerate its meaning. However, this problem is directly related to the failure of the user of the 

terminology to fully understand the meaning. One of the challenges which is in some ways unique 

to forensic science is the fact that the end users and some analysts often do not have scientific 

backgrounds and do not regularly use the language of science. Law enforcement, lawyers and 

judges need to learn the language; inconsistent terminology within and across disciplines further 

compounds this challenge. When lawyers misconstrue terms, they may unintentionally mislead 

others. In Williamson, for instance, the prosecutor argued in closing, to the jury, in respect to the 

hair evidence, “there’s a match.”18 This statement completely misrepresented the expert testimony

and ignored the limitations of the technique. Given the term “match” is also commonly understood 

as the kind of “match” popularly associated with fingerprints or DNA profiles, the statement 

becomes even more damaging.19 Again, would having had a clear and concise definition originally 

for the value of this evidence avoided these problems? It is very hard to say, but it would be a step 

forward to have a clearly defined, uniform term which is properly articulated. There are more than 

one set of challenges that lead to an example such as this. One study suggested that presentation 

of the limitations of forensic science during trial through cross-examination or jury instructions 

might do very little to cure the problems surrounding overstatement in the courtroom.20 But, having 

 

well as others are designed only to assist practitioners in further improving communication and the overall practice 

of Forensic Science, something this Commission is deeply committed to. 

17 Williamson, 904 F.Supp. at 1554.

18 Williamson, 904 F. Supp. At 1557.

19 Two studies suggest that this is how jurors and college students tend to interpret it. See McQuieston-Surett &

Saks (2009) (potential jurors); Dawn McQuieston-Surrett & Michael J. Saks, Communicating Opinion Evidence in 

the Forensic Identification Sciences: Accuracy and Impact, 59 Hastings L.J. 1159 (2008) (students).

20 See Dawn McQuieston-Surett & Michael J. Saks, The Testimony of Forensic Identification Science: What Expert 

Witnesses Say and What Factfinders Hear, 33 Law & Hum. Behav. 436, 451 (2009)(“These results should give pause 
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terminology which is clearly defined in a written, standardized format might assist those charged 

with these responsibilities into imposing limits on how terms are used.

Forensic terminology must also be understood by juries and the public. Even an explicit definition 

and statement may not be fully appreciated when terminology deviates from common usage. An 

example comes from a study that looked at language adopted by the American Board of Forensic 

Odontology to encourage their members to use particular terms to express their conclusions.21 The 

Board defined the terms, Reasonable Scientific Certainty, Probable, Consistent (with) and Match 

to express the highest to lowest degree of similarity in a comparison analysis.22 When researchers 

asked undergraduate students to rank these terms, without being provided the ABFO’s definitions, 

most of the students put “Match” at the top of the list.23 When a term commonly used and 

understood is redefined to have a conflicting technical meaning, the common understanding may 

stand in the way of comprehension and correct application.

This type of inconsistency can lead to great misunderstanding. Since many of the terms found in 

reports are used to make decisions about a case outside of the courtroom and often without

consultation with the report writer, such as whether to further investigate, charge a suspect or enter 

into a plea bargain, consideration must be given to whether terminology is also consistent with its 

general, non-forensic use. In some ways this is much like the standardization work done by those 

involved with the VIM in standardizing across disciplines, such as chemistry and biology, when 

expressing measurement. 

Another example of this kind of challenge is the word “reliability.” “Reliability” in science refers 

to the precision, consistency, reproducibility, limitations and bias of an experiment. In law, 

“reliability” is describing a level of “trustworthiness, or worthy of confidence.”24 Neither is 

incorrect, but the inconsistent use of these terms can and does cause miscommunication. 

Creating consistent terminology within a discipline and among multidisciplinary groups will not 

solve every misunderstanding between science and the law but, as the scientific community has 

discovered, “consistent definitions of concepts within their associated terms and symbols are 

essential if analysts and customers across the globe are to understand each other.”25

 

to anyone who believes that the traditional tools of the adversarial process (e.g., cross-examination, opposing 

experts, instructions) will readily undo the effects of misleading expert testimony.”)

21 Dawn McQuiston-Surrett & Michael Saks, Communicating Opinion Evidence in the Forensic Identification 

Sciences: Accuracy and Impact, 59 Hastings L.J. 1159 2007 -2008.

22 The definitions at the time were, “reasonable scientific certainty” means the “highest order of certainty; no 

reasonable probability of error:” “Probable” means “more likely than not; most people could not leave such a 

mark:” “Consistent (with) meaning “similarity, but no degree of specificity, like match; may or may not be:” 

“Match” is “some concordance, some similarity, but no expression of specificity intended; generally similar but 

true of a large percentage of the population.” Id. at 1162, table 1. 

23 Id.

24 Black’s Law Dictionary.

25 V J Barwick and E Prichard (Eds), Eurachem Guide: Terminology in Analytical Measurement – Introduction to VIM 

3 (2011). 
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There are a multitude of other examples of inconsistent terminology in all areas of forensic 

practice. The intent of this document is to set the stage for robust debate and empower the forensic 

community to rely on well defined, consistent terminology that is ubiquitous and generally 

acceptable. This in turn can assist practitioners responsible for communicating this information to 

better express their findings and analyses to a non-scientific audience. Ultimately, this work should 

provide clarity and guidance for all users within the forensic science and the legal system, who in 

the end, share the responsibility of learning, understanding and properly using these terms in the 

art of persuasion.