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Scientific & Technical Review 

Panel 

Final Report for

OSAC 2022-S-0024

Best Practice Recommendations

for Evaluative Forensic DNA

Testimony 

Organization of Scientific Area Committees (OSAC) for Forensic Science
 

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STRP Final Report

OSAC 2022-S-0024 

Best Practice Recommendations for

Evaluative Forensic DNA Testimony 

Organization of Scientific Area Committees (OSAC) for Forensics Science

July 11, 2023 

Disclaimer:

This report was produced by an independent Scientific and Technical Review Panel (STRP). The 

views expressed in the report do not necessarily reflect the views or policies of the U.S. 

Government. Visit the OSAC website for more information on OSAC’s STRP process. 

Scientific & Technical Review Panel Members

• Hillel Bavli, SMU

• Frederick R. Bieber, Harvard Medical School

• Sara Walker, Intermountain Forensics

• Jonathan Koehler, Northwestern University

• Greggory LaBerge, Denver Police Department

• Susan Pope, Principal Forensic Services

• Adele Quigley-McBride, Duke University

• Tiffany Roy, ForensicAid

• Joel Sutton, USACIL

• Sandy Zabell, Northwestern University
 

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Report Summary:

The Scientific and Technical Review Panel (STRP) for “Best Practice Recommendations for 

Evaluative Forensic DNA Testimony” is an independent panel appointed by the National 

Institute of Standards and Technology (NIST). A STRP is established with a range of experts to 

consider how well a standard meets the needs of the forensic science, law enforcement, and legal 

communities, and to recommend improvements to the standards under review. The STRP 

appreciates the efforts of Tim Kalafut, Human Forensic Biology Subcommittee member, while 

serving as the subcommittee liaison to this STRP during the review process. 

The STRP began its review process with a kickoff meeting on February 11, 2022, and concluded 

with this STRP final report. The panel reviewed the draft standard and prepared comments for 

the Human Forensic Biology Subcommittee. 

Report Components:

The STRP reviewed this draft standard against OSAC’s STRP Instructions for Review which 

include the following content areas: scientific and technical merit, human factors, quality 

assurance, scope and purpose, terminology, method description and reporting results. The details 

below contain a brief description of each reviewed content area and the STRP’s assessment of 

how that content was addressed in the draft OSAC Proposed Standard. 

1. Scientific and Technical Merit: OSAC-approved standards must have strong scientific 

foundations so that the methods practitioners employ are scientifically valid, and the 

resulting claims are trustworthy. In addition, standards for methods or interpretation of 

results must include the expression and communication of the uncertainties in measurements 

or other results.

1.1 Consensus View - Upon review, the STRP believes that the proposed Best Practice

Recommendation (BPR) serves to address an important topic and is based on a 

logical framework well-characterized in the global forensic community. This

framework, known as the “hierarchy of propositions”, is intended to assist the 

scientist with when and how to properly evaluate the DNA results during expert 

testimony while considering the key question being asked and its implications in a 

Note Regarding Supplemental Comments – This STRP Report includes

“Comments submitted during the voting process” that represent the view(s) 

of an individual(s). The comments were proposed after the STRP discussion 

was completed, and therefore, were not subjected to discussion amongst the 

STR panelists. All the comments submitted for the respective sections are 

included to ensure the views of the STR panelists are accurately represented.
 

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judicial setting. For example, the proposed BPR rightly points out that moving up 

the hierarchy (e.g., sub-source to activity level questions) requires more case

information and expert knowledge. The proposed BPR also provides practical

applications of the method in “Supporting Information” and through the use of realworld case examples. Uncertainty with this method is explicitly expressed through 

the use of conditional probabilities as described in the document. 

Although the BPR attempts to address all levels of the hierarchy of propositions 

encountered in forensic DNA analysis, the STRP recognizes the differing

probabilistic and statistical issues that arise at each level of the hierarchy; from subsub-source to sub-source, to source, and to activity and crime levels.

Accordingly, the STRP recommends that activity and crime level propositions 

should be handled separately in a stand-alone document. This would best provide 

guidance through both a framework and discussion of reporting requirements and 

testimony guidelines. Research is lacking for many conclusions and opinions 

that could arise from these types of analyses. Therefore, it would be a service to the 

forensic DNA community to handle such issues separately in detail to

avoid confusion in the current document between the levels of hierarchy. 

1.2 Minority View - This alternative view concurs with the implicit suggestion in the 

Consensus View noted above that activity and crime level propositions should not 

be part of the “Best Practice Recommendations for Evaluative Forensic DNA 

Testimony.” But this alternative view takes the position that the focus in the 

document on activity level propositions is misplaced. Instead, the focus should be 

on providing weight of evidence testimony for source propositions alone. A source 

proposition (e.g., “Whose DNA is on the knife?”) lends itself to scientific weight of 

evidence testimony in the form of empirically validated conditional probabilities. 

This is not the case for an activity level proposition (e.g., “How did the defendant’s 

DNA get on the knife?”). The problem is not with the logic of the hierarchy of 

propositions framework. Rather, the problem is with the absence of statistical 

databases that speak to the creation of the conditional probabilities of interest when 

dealing with activity level propositions. A DNA examiner could be in a 

scientifically tenable position to estimate the probability of seeing an evidentiary 

DNA profile that matches a defendant’s own DNA profile given that the defendant 

is not the source of the evidentiary DNA. However, the examiner cannot be in a 

similar position to estimate the probability of seeing matching DNA profiles given 

that the match was the result of transfer from the hand of a different person who 

held the knife. In the former case (source level), databases can be constructed, 

consulted, and subject to examination at trial. In the latter case (activity level), there 

would be no such databases, and therefore the basis for an examiner’s conditional 

probabilities related to the activity level propositions would not rest on firm footing 

and would likely be idiosyncratic. 

1.3 Comment Received During Voting - The Consensus View requires a minor, but

important, modification to be acceptable: Add a sentence that explicitly rejects 
 

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speculative testimony regarding probabilities for activity-level propositions in the 

absence of empirical support or a substantial logical basis.

1.4 Comment Received During Voting - DNA analysts should never address the 

offense/crime level. This is the province of the trier. This document appropriately 

addresses sub-source and sub-sub source level evaluations. It should be noted that 

evaluations on these levels are absolutely required by accreditation to be included in 

written, technically reviewed and administratively reviewed reports. This document 

should break out evaluation of findings at the source level and activity level as 

separate documents because we are currently not operating at those levels of the 

hierarchy in the U.S. and more guidance will be required. 

The title of this document would need to change in order for the good parts to stay 

and the bad parts to go. As a suggestion, "Evaluations of findings given sub-sub 

source and sub-source level propositions."

2. Human Factors: All forensic science methods rely on human performance in acquiring, 

examining, reporting, and testifying to the results. In the examination phase, some standards 

rely heavily on human judgment, whereas others rely more on properly maintained and 

calibrated instruments and statistical analysis of data.

2.1. Consensus View - Although the subcommittee has worked hard to address issues 

that stem from human factors concerns, there are still several serious problems that 

remain in the standard. The two main human factors concerns are noted here. 

First, the document does little to incorporate the existing empirical research on how 

to communicate forensic evidence, such as results of DNA comparisons, to judges 

and jurors effectively. Communicating complex information so that it can be 

understood by the factfinder is one of the primary goals of expert testimony, so it is 

a serious oversight for the subcommittee to ignore an entire body of work 

addressing exactly that issue. For instance, the only empirical article from human 

factors researchers that is provided in this standard is more than three decades old 

(Thompson and Schumann, 1987). There are many studies examining how people 

understand likelihood ratios or verbal equivalents in the context of forensic 

testimony, but none of these are cited in the document or the normative references 

(e.g., Martire et al., 2014: https://doi.org/10.1016/j.forsciiint.2014.04.005). The 

recommendations contained in many of these articles, at times, run counter to the 

recommendations in the standard. For example, the standard advocates for the use 

of verbal equivalents in testimony, which has little empirical support from statistics 

and human factors research. Words can mean different things to different people 

and research suggests that using equivalents can mislead jurors rather than clarify 

the value of the results.

Second, the document allows for a single analyst to perform complex analyses on 

the stand without time to prepare, consider all factors, and conduct research. Results 

relevant to activity-level propositions require specific, higher-level experience and 
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training before an analyst can perform those analyses and interpret those results 

appropriately. In addition, part of that experience and training involves knowing 

when it is inappropriate to even attempt an analysis at the activity-level. Given the 

multitude of factors that can influence transfer, persistence, and other activityrelevant circumstances, these analyses are far too complex to be done on the stand 

and, in many cases, too complicated and uncertain to be done at all. From the 

perspective of a human factor’s researcher, the strong effect of such statements on 

the fact finder and chance of error and bias is too high for it to be acceptable for 

DNA analysts to engage with activity-level hypotheticals on the stand with no 

preparation, and no technical or quality review, verification, or other oversight. 

One way to reduce these human factors concerns would be to have a training 

standard designed to arm analysts with the necessary knowledge and experience to 

perform these analyses correctly (and also know when they are inappropriate), as 

well as test their ability to do these analyses. The required training and expertise to 

perform these types of analyses are separate and distinct from the expertise that is 

required to perform evaluations of findings on the lower levels of the hierarchy, a 

fact that U.S. DNA analysts may not intuitively know.1 There would also need to be 

a standard guiding analysts’ evaluation and reporting procedure for DNA findings 

given proposed activities. Such a standard would specify the supporting notes and 

data to be provided alongside the evaluation, as well as the procedure for technical 

and administrative review of the work prior to testifying to activity-level results.

2.2. Minority View - Many laboratories in the U.S. have taken steps to move toward 

evaluation of DNA profiles given sub-source level propositions. Labs that have 

implemented STRmix and the likelihood ratio should already be familiar with the 

well-established framework of the Hierarchy of Propositions, first described by 

Cook et. al in 1998.2 This STRP feels this document has significant merit in 

clarifying for the community the framework for performing evaluations of DNA 

findings given proposed activities, including clarifications on how to avoid common 

pitfalls such as the prosecutor’s fallacy. There were some discussions regarding 

language and definitions for clarity from a human factors perspective, but the 

overall STRP was supportive of the document as it applies to sub-sub-source, subsource and source level evaluations of DNA results given propositions on these 

levels.

2.3. Comment Received During Voting - The draft BPR addresses a number of

important human-factors concerns. However, there are serious concerns that have 

not been adequately addressed. For example, the draft standard does not account for 

a body of recent literature regarding how people understand likelihood ratios or 

1 Roland A.H. van Oorschot, Bianca Szkuta, Kaye N. Ballantyne, Mariya Goray, Need for dedicated training, 

competency assessment, authorizations and ongoing proficiency testing for those addressing DNA transfer issues, 

Forensic Science International: Genetics Supplement Series, Volume 6, 2017,Pages e32-e34, ISSN 1875-1768, 

https://doi.org/10.1016/j.fsigss.2017.09.013.

2 R. Cook, I.W. Evett, G. Jackson, P.J. Jones, J.A. Lambert, A hierarchy of propositions: deciding which level to 

address in casework, Science & Justice, Volume 38, Issue 4, 1998, Pages 231-239, ISSN 1355-0306, 

https://doi.org/10.1016/S1355-0306(98)72117-3.
 

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verbal expressions of such measures in the context of forensic testimony. This 

literature arguably runs counter to certain recommendations in the standard. In 

addition, while the draft standard focuses heavily on how an expert should phrase a 

statement to avoid transposing a conditional, it arguably does not adequately focus 

on phrasing testimony such that jurors, judges, attorneys, and other legal actors will 

not misunderstand the testimony so as to transpose a conditional. Finally, the BPR 

seems to support the use of notional probabilities and other testimony regarding 

activity-level propositions that are not necessarily based on firmly grounded data. 

The draft BPR seems to substantially underestimate the danger of jurors attaching 

undue weight to and otherwise misusing this evidence.

3. Quality Assurance: Quality assurance covers a broad range of topics. For example, a 

method must include quality assurance procedures to ensure that sufficiently similar results 

will be obtained when the methodology is properly followed by different users in different 

facilities. 

3.1. Consensus View - A process for the provision of an evaluative expert opinion 

and testimony on DNA activities must include quality assurance that:

• The process follows the recognized framework for casework assessment and 

interpretation and has been validated by a suitable accreditation body for the 

laboratory and experts using it. 

• The robustness of the expert’s opinion sits on a base of verified data, 

applicable published, or publicly available validation studies, as well as 

demonstrable recorded experience. 

• The initial results and verification of those results are both considered equally 

important when reviewing the evidence. 

This STRP finds that there are still several elements that need to be addressed from 

a quality assurance perspective. Specifically, without guidance for training and 

assessment, as well as feedback on use of this framework, there are no provisions in 

this document for assuring the quality of its use. 

There are also potential quality assurance issues associated with analysts engaging 

with hypotheticals on the stand and performing analyses (in particular, activity-level 

analyses) during testimony. This would be equivalent to reporting/ testifying to 

analyses that have not been through quality review or technical review. In addition, 

activity-level analyses require a level of specialized training not typically offered or 

undertaken by analysts in the U.S. (or even internationally), so there remains 

questions about whether analysts are trained and accredited to perform these 

analyses even in the lab, let alone while on the stand. These analyses often also lack 

the necessary published data and recorded experience to support the findings. 

3.2. Minority View - Quality assurance topics are properly covered in this draft 

standard. There are references for international standards and guidelines giving 

advice on suitable validation processes including risk assessment, setting user 
 

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requirements, specifications and acceptance criteria for a subjective evaluation 

process.

3.3. Comment Received During Voting - The Consensus view must incorporate a 

recommendation regarding communication of relevant error rate information and 

estimates to triers of fact.

4. Scope and Purpose: Standards should have a short statement of their scope and purpose. 

They should list the topics that they address and the related topics that they do not address. 

Requirements, recommendations, or statements of what is permitted or prohibited do not 

belong in this section.

4.1. Consensus View - Upon review, the STRP believes that the “Scope” of the 

document is clearly detailed as written but does not include a specific “Purpose” 

statement. The “Foreword” does provide an excellent summary of background 

information to include the underlying scientific principles behind the framework 

needed for evaluative forensic DNA testimony. The purpose is addressed at length 

in this same section beginning with the second sentence (line 2) and further 

summarized with the “goal” (lines 72-74). Perhaps a single purpose statement could 

be added under the “Scope” section using this same language from the “Foreword”. 

Annex A (supporting documentation) is an important section in this proposed BPR 

as it often provides the needed detail and basis for many of the recommendations 

listed. It should be mentioned in the foreword with its purpose to better direct the 

reader for the appropriate context with each recommendation. Currently, the 

foreword only mentions the recommendations (lines 76-82). 

4.2. Comment Received During Voting - Recommended Modification to the 

Consensus View – Add the following: "Best practice is to include the evaluation of 

DNA evidence given activity level propositions in a laboratory report. This will 

allow for any required technical reviews of the findings that would be reported on 

the witness stand. However, currently very few laboratories are including this in 

their reports, yet questions regarding activity level propositions show up routinely 

in trials. The goal of this document is to address immediate needs for best practices 

in testimony when the expert witness is not given the opportunity to 

provide their results in a written report, and how to communicate both the 

evaluation and the limitations of that evaluation." 

If the expert has not been given the opportunity to provide their results in a written 

report, they should not be performing these types of high-level analyses, especially 

on the witness stand. Evaluations of findings given proposed activities require 

formal consideration far beyond what would be possible during a testimony. 

5. Terminology: Standards should define terms that have specialized meanings. Only rarely 

should they give a highly restricted or specialized meaning to a term in common use among 

the general public.
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5.1. Consensus View - The STRP finds that the draft standard requires substantial 

revision with respect to its terminology. First, the draft fails to define the term 

“notional probability.” The intended meaning and substantive application of 

notional probabilities are fundamental to the scientific and technical merit of the 

draft and should be defined and explained carefully. 

Second, while the draft correctly emphasizes the substantial risk of experts, 

attorneys, and other legal actors inadvertently transposing a conditional or of 

presenting testimony in a way that jurors are likely to transpose a conditional—that 

is, to confuse the probability of A given B as the probability of B given A—it 

makes the mistake of equating a “transposed conditional” with the “prosecutor’s 

fallacy.” These are distinct concepts—with the prosecutor’s fallacy being a 

particular type of transposed conditional—and should be treated as such in the draft. 

Third, the draft frequently includes unnecessarily extreme language—for instance, 

“It is always desirable to put things in terms of probability”; “It is logically 

meaningless to suggest that any evidence has value in itself as support for any 

particular proposition in isolation”; It is “not useful,” or “mathematically 

meaningless,” to say that something is “possible.” Reasonable scientists could, and 

likely would, disagree with some of these statements. For purposes of accuracy and 

buy-in, the draft should employ more moderate language—and adopt more flexible 

positions (e.g., lines 932-35: “the expert should be cautious of assigning a 

probability of 1 or 0”). 

Fourth, and relatedly, the draft should adopt a more flexible position regarding an 

expert’s response to questions about whether something is “possible.” Although the 

STRP consensus view agrees that one’s acknowledgment that something is 

“possible” generally has little probative value, depending on the circumstances, it 

may be appropriate for the expert to answer the question and consider providing 

further explanation. In addition, the “note” that accompanies the definition of the 

term “possible” (lines 249-53) should be removed. 

Fifth, the concept of a “verbal scale” for communicating a likelihood ratio should 

be defined and developed more fully. The intended meaning and substantive 

application of such scales are fundamental to the scientific and technical merit of 

the draft, and the utility of any qualitative terms employed to describe various 

ranges of likelihood ratios should have empirical support or a substantial logical 

basis.

5.2. Comment Received During Voting – One commenter agrees with this view and 

further; DNA has always been the gold standard because we have avoided the use 

of subjective, personal and notional terms. We have always applied frequencies 

derived from scientific study to our sub-source and sub-sub source analysis. 

Firearms and toolmarks and fingerprints have worked for the last decade to move 

away from notional language for reporting the weight of a comparison. Why would 
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we allow this backslide in DNA at the highest level of analysis that we can possibly 

evaluate evidence on?

Notional probabilities could not be applied to sub-sub source and sub source level 

analyses because that would violate accreditation standards and legal case law. 

Numerical probabilities will also be required to accompany source and activity level 

evaluations. One of the STRP members raised concerns over the verbal scale 

because it has no statistical support for it’s use, and I would make the same 

argument against notional probabilities. The term should be removed from this 

document and from DNA lexicon, in my opinion.

6. Method Description: There is no rule as to the necessary level of detail in the description of 

the method. Some parts of the method may be performed in alternative ways without 

affecting the quality and consistency of the results. Standards should focus on standardizing 

steps that must be performed consistently across organizations to ensure equivalent results. 

Alternatively, standards can define specific performance criteria that are required to be 

demonstrated and met rather than specifying the exact way a task must be done. For example, 

it may be enough to specify the lower limit for detecting a substance without specifying the 

equipment or method for achieving this limit of detection.

6.1. Consensus View – Upon review, the STRP believes that the proposed BPR 

addresses a well-described, scientifically sound, and comprehensive method. 

However, in regard to reporting results with this method there are concerns with the 

noted differences with the models mentioned for assigning probabilities to the LRs 

that will be reported for DNA results given source level and activity level 

propositions. For source level propositions, Recommendation 4.3.1.1.1 does not 

give a description of the model to be used. Recommendation 4.3.2.1 later describes 

a process for how to use probabilities or an LR to communicate source level 

findings, but it is still unclear on the model itself for how these probabilities are to 

be assigned. A better description of the model (e.g., Bayesian networks) should be 

included here along with any published references. 

For activity level propositions, the STRP has similar concerns with 

Recommendation 4.4.2.1 and the subsequent “Note” as written. This proposed BPR 

states that one may use a model (not defined) or may use notional or personal 

probabilities. This potentially conflicts with the ISFG recommendations (2020) 

which state that whenever possible, relevant published data should be used. In the 

absence of published data, calibrated experience, case-tailored experiments, and 

peer consultation can be used but this is not intended to be “personal” to the 

scientist. Instead, ISFG emphasizes that it is the responsibility of the scientist to 

represent the view of the community of scientists such that similar views would be 

expected by other informed individuals as far as it is possible. If notional 

probabilities are to be used in the LR that will be reported, they must be 

accompanied by data sources that can be independently reviewed which support 

these probabilities. 
 

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The proposed BPR also notes in 4.4.2.2 that the LR should be communicated 

numerically OR by using a qualitative verbal statement. If a verbal statement is to 

be used, it must come with the assignment of a numerical LR as mentioned with 

sub-sub-source, sub-source, and source level LRs. Again, the ISFG 

recommendations (2020) state that a verbal scale is optional but cannot be used by 

itself for evaluating DNA results considering activity level propositions. 

The methodology described in this document of rendering conclusions on the 

activity level while testifying is not in line with the guiding principles of 

interpretation: balance, logic, robustness and transparency. Laboratories in the 

U.S. commonly report at the sub-sub-source or sub-source level. At the sub-sub 

source, sub-source and source levels of the hierarchy, we recognize that we would 

perform all analysis in advance of trial, write reports, submit our work for technical 

and administrative review and issue a written statement describing our opinions, in 

line with common accreditation standards. So, the recommendation to perform 

analysis at an activity level is concerning. The provisions in the activity level 

section including evaluations of findings given proposed activities for the first time 

in court and ad-hoc assignment of notional probabilities that do not involve 

frequencies or calculations are not robust. This practice does not allow for an 

expert to research literature, locate relevant data or perform experiments. Another 

qualified analyst does not review this analysis to ensure it is scientifically sound, 

which is not transparent. Relying on unspecified training and experience, as well 

as unspecified resources, is not recognized by the scientific community or the 

normative references listed in this document.3

 The suggested diversion from 

published, recognized best practices for communicating evaluations of findings 

given proposed activities to address a perceived knowledge gap requires revision 

and further discussion before it is suitable to publish as a standard.

6.2. Minority View – This draft section touches on important points but requires 

simplification. For example, the description can be simplified to say as follows: The 

draft BPR applies a scientifically sound and well-grounded method. However, it is 

concerning in a number of respects. First, the draft BPR is vague in its descriptions 

of models for assigning probabilities—e.g., for source-level propositions in section

4.3.1.1.1 (see also section 4.3.2.1) and activity-level propositions in section 4.4.2.1. 

Second, the draft BPR seems to support the use of notional probabilities without 

providing a well-supported empirical basis for such testimony. The STRP views 

this as problematic and arguably contrary to accepted principles and practices (see, 

e.g., 2020 ISFG recommendations). Similarly, the draft BPR supports the use of 

qualitative verbal statements as an alternative to numerical expressions of 

likelihood ratios. However, the BPR does not provide or require a well-supported 

3 DNA commission of the International society for forensic genetics_ Assessing the value of forensic biological 

evidence - Guidelines highlighting the importance of propositions. Part II_ Evaluation of biological traces 

considering activity level propositions (isfg.org): “Whenever possible, relevant published data should be used. The 

source of the knowledge should be disclosed and the limits of the data discussed. In the absence of published data, 

calibrated experience, case tailored experiments, peer consultation can be used. In any case, the use of the data 

needs to be justified and the expert should be transparent on the limitations of the data. Viewpoints, based solely on 

personal casework experience should be avoided.” 
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empirical basis for such standalone expressions. The STRP views this as 

problematic and arguably contrary to accepted principles and practices (see id.).

7. Reporting Results: Methods must not only be well described, scientifically sound, and 

comprehensive but also lead to reported results that are within the scope of the standard, 

appropriately caveated, and not overreaching.

7.1. Consensus View – The STRP believes that this standard only provides substantive 

guidance for reporting via verbal communication of results in testimony. Although 

the written reports are mentioned throughout as a supplement to verbal 

communication/testimony, there are no requirements or guidelines in this document 

to help analysts and laboratories with formal report writing, required components of 

written reports, and the requirement of peer review. The standard also does not refer 

the reader to another standard or document where such guidance can be found. 

For the reasons already described in the Methodology section of this STRP report, 

any opinions not reported in a formal written report and disclosed to both legal 

parties in advance of trial should not be considered robust, transparent, or legally 

admissible. The STRP believes that the framework described in this standard could 

be misused if there is no accompanying requirements or guidance for the written 

reports on the results that form the basis for such testimony. 

In addition, there needs to be an adequate description of who should and should not 

be using the framework outlined in the standard, and clear definitions about when 

this framework should and should not be used. Without these elements, there is a 

serious risk of personnel testifying to results that they are not trained to complete, or 

testifying to results that have not undergone formal review or formal reporting 

procedures. In addition to potentially leading to miscarriages of justice, this would 

do little to change the recognized training gap that exists presently—the gap this 

standard seeks to address. In fact, it may actually exacerbate the issues that arise 

from the training gap. 

If the subcommittee intends any guidance on formal report writing and associated 

elements to be left out of this proposed BPR, then this should be stated in the 

“Scope” for clarity, especially given there are references to formal reports in the 

document itself. The same is true for any training and authorization required for a 

DNA scientist to use this method—this is also noticeably absent and necessary for 

appropriate application of the guidance in this standard. For example, adding 

language to the Scope indicating that “this standard was not created to provide 

guidance on formal written reports that should be used to support the testimony 

described in this framework, or the training and assessment that should occur before 

an analyst employs this framework when giving testimony. These necessary 

elements are outside the Scope of this document and should be addressed by the 

laboratory prior to encouraging analysts to apply this framework to their oral 

communication of their results.”
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7.2. Minority View - This section touches on important points but requires 

simplification and modification. For example, the description can be simplified and 

narrowed (although with one additional point) to say as follows: The draft BPR 

provides guidance for reporting results via testimony. There is a significant 

potential for misuse in the absence of guidance for written reports that form the 

basis of such testimony. The draft BPR does not refer the reader to other standards 

or sources for such guidance, and it does not adequately address written 

components of an expert’s analysis. The BPR should clarify its intended scope in 

this regard and should discuss the importance of a written report with respect to an 

expert’s testimony. In addition, as suggested above, the STRP finds problematic the 

draft BPR’s support of an expert’s use of notional probabilities and standalone 

qualitative verbal statements to describe likelihood ratios. Testimony in this regard 

in the absence of a firm empirical basis is problematic and arguably contrary to 

accepted principles and practices (see id.). Finally, the draft BPR provides 

inadequate clarity regarding when and by whom the framework described in the 

draft BPR should be used.

Comment Received During Voting - The BPR needs to be explicit about how 

weight of evidence should be described to maximize the chance that triers of fact 

understand the value of the evidence.