FINAL by: OSAC Program Office; Version 2, January 13, 2020 1 

OSAC RESEARCH NEEDS ASSESSMENT FORM 

Title of research need: Best practices for reporting likelihood ratios or other probabilistic results 

in court 

Describe

the need:

The criminal justice system requires all positive associations of forensic unknowns to a 

probative reference sample to be accompanied by a meaningful statistical weight that 

is readily understood by jurors and the legal community. There are different 

approaches to derive statistical significance estimates for positive associations, most or 

all of which can be difficult to explain to a jury and/or a judge. Current thinking favors 

likelihood ratios and probabilistic genotyping results, especially for complex mixtures.

Research should target how forensic scientists can best present statistical weight 

based on likelihood ratios or other probabilistic statistics in an unbiased manner. 

Additionally, how this information is perceived by legal professionals and the jurors 

should also be evaluated. Research should include an assessment of the utility of verbal 

scales and evaluate the possible need for additional metrics and other tools to add 

context to a probabilistic value. 

Keyword(s): Testimony, likelihood ratio, probabilistic statistics

Submitting subcommittee(s): Human Biology Date Approved: 05/04/2021

(If SAC review identifies additional subcommittees, add them to the box above.)

Background Information:

1. Does this research need address a gap(s) in a current or planned standard? (ex.: Field identification system 

for on scene opioid detection and confirmation)

It coincides and supports with standards that are in the review process 

2. Are you aware of any ongoing research that may address this research need that has not yet been published 

(e.g., research presented in conference proceedings, studies that you or a colleague have participated in but 

have yet to be published)?

Yes 

3. Key bibliographic references relating to this research need: 

1) Arscott, E., Morgan, R., Meakin, G., & French, J. (2017). Understanding forensic expert evaluative 

evidence: A study of the perception of verbal expressions of the strength of evidence. Science and

Justice, 57(3), 221–227. 

http://doi.org/10.1016/j.scijus.2017.02.002 

2) de Keijser J, Elffers H (2012) Understanding of forensic expert reports by judges, defense lawyers 

and forensic professionals. Psychology, Crime & Law 18(2):191-207. 

https://doi.org/10.1080/10683161003736744
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3) Howes, L. M. (2015). The communication of forensic science in the criminal justice system: A review 

of theory and proposed directions for research. Science & Justice, 55(2), 145–154. 

http://doi.org/10.1016/j.scijus.2014.11.002 

4) Mullen, C., Spence, D., Moxey, L., & Jamieson, A. (2014). Perception problems of the verbal scale. 

Science & Justice, 54(2), 154–158. 

http://doi.org/10.1016/j.scijus.2013.10.004 

5) Taroni, F., Bozza, S., Biedermann, A., & Aitken, C. (2016). Dismissal of the illusion of uncertainty in 

the assessment of a likelihood ratio. Law, Probability and Risk, 15, 1–15. 

http://doi.org/10.1017/CBO9781107415324.004

6) Thompson, WC, Newman, EJ (2015) Lay understanding of forensic statistics: Evaluation of random 

match probabilities, likelihood ratios, and verbal equivalents. Law and Human Behavior 39(4):332–

349. 

https://doi.org/10.1037/lhb0000134

4. Review the annual operational/research needs published by the National Institute of Justice (NIJ) at 

https://nij.ojp.gov/topics/articles/forensic-science-research-and-development-technology-working-groupoperational#latest? Is your research need identified by NIJ?

No 

5. In what ways would the research results improve current laboratory capabilities? 

Scientific results in a criminal case need to be communicated completely, clearly, with appropriate 

statistical weight, and in a fashion that is not misinterpreted by legal professionals and jurors. Best 

practices on how to communicate statistical relevance, specifically using complex concepts such as 

likelihood ratios or other probabilistic statistics would support laboratories and make report writing 

and testimony more effective and easily comprehensible. 

6. In what ways would the research results improve understanding of the scientific basis for the 

subcommittee(s)? 

The Human biology subcommittee is interested in how DNA results requiring likelihood ratios and 

probabilistic statistical evaluation are perceived by criminal justice stakeholders and jury members. 

This borders on cognitive science but is directly relevant to our field as well as to other fields of 

forensic science who are also evaluating probabilistic approaches

7. In what ways would the research results improve services to the criminal justice system? 

Scientific results in a criminal case need to be communicated completely, clearly, with appropriate 

statistical weight, and in a fashion that is not misinterpreted by legal professionals and jurors. Best 

practices on how to communicate statistical relevance would help prevent the misinterpretation/ 

misrepresentation of data in court and improve the ratio of justified versus wrongful convictions. 
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8. Status assessment (I, II, III, or IV): II

Major gap in 

current 

knowledge 

Minor gap in 

current 

knowledge 

 

 No or limited

current research is 

being conducted I III 

 Existing current 

research is being 

conducted II IV 

This research need has been identified by one or more subcommittees of OSAC and is being provided as an

informational resource to the community.