Is “common sense” enough for a jury to consider expert testimony? (min version)

(Welcome to my A/B test. For the other version of this post, click here.)

As I’ve previously noted, the 2009 NAS report on forensic science has revolutionized fingerprint identification and a number of other forensic disciplines.

One part of this revolution was the Department of Justice 2018 document entitled “UNIFORM LANGUAGE FOR TESTIMONY AND REPORTS FOR THE FORENSIC LATENT PRINT DISCIPLINE.” A PDF version of the report can be found here.

This document applies to Department of Justice examiners who are authorized to prepare reports and provide expert witness testimony regarding the forensic examination of latent print evidence.


Based upon the NAS report and subsequent efforts, Part IV of the DOJ document (“Qualifications and Limitations of Forensic Latent Print Examinations”) sets some clear guidelines about how a latent print examiner should describe his or her findings.


So a pre-2009 latent print examiner who appeared in court and said “I am 100% certain that these two fingerprints belong to the same person, to the exclusion of all other persons, because I have never been wrong in the last 25 years” would fail the 2018 DOJ criteria.

But would a jury know that?

That’s what CSAFE discussed in a recent post, “AAFS 2022 RECAP: UNDERSTANDING JUROR COMPREHENSION OF FORENSIC TESTIMONY: ASSESSING JURORS’ DECISION MAKING AND EVIDENCE EVALUATION.” Feel free to read the entire article, or if you like you can read my “succinct” excerpt from two portions of the article:

Koolmees and her colleagues examined whether jurors could distinguish low-quality testimony from high-quality testimony of forensic experts, using the language guidelines released by the Department of Justice (DOJ) in 2018 as an indicator of quality….

Only when comparing the conditions of zero guideline violations and four and five violations were there any changes in guilty verdicts, signifying jurors may notice a change in the quality of forensic testimony only when the quality is severely low.


So this raises the question of whether the NAS report, for all of its revolutionary effects, will have any true results in courtroom testimony.

  • Will jurors heed the advice from the DOJ guidelines to accurately consider the testimony of a forensic expert?
  • Or will the jurors’ “common sense,” based on old Perry Mason and C.S.I. TV shows, prevent jurors from consiering expert testimony in the correct light?

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