Source Attribution as an Ultimate Opinion

An interesting new article is available from David H. Kaye in Jurimetrics: The Journal of Law, Science and Technology Vol. 60, No. 2, Winter 2020.

Abstract
For decades, scientists, statisticians, psychologists, and lawyers have urged forensic scientists who compare handwriting, fingerprints, fibers, electronic recordings, shoeprints, toolmarks, soil, glass fragments, paint chips, and other items to change their ways. At last it seems that “[t]he traditional assumption that items like fingerprints and toolmarks have unique patterns that allow experts to accurately determine their source . . . is being replaced by a new logic of forensic reporting.” With the dissemination of “probabilistic genotyping” software that generates “likelihood ratios” for DNA evidence, the logic is making its way into US courts.

Recently, the Justice Department’s Senior Advisor on Forensic Science commented on a connection between prominent statements endorsing the new logic and an old rule of evidence concerning “ultimate issues.” He suggested that “some people . . . would like to pretend that [Federal Rule of Evidence 704] doesn't exist, but it actually goes against that school of thought.” This essay considers the nexus between Rule 704 and forensic-science testimony, old and new. It concludes that the rule does not apply to all source attributions, and even when it does apply, it supplies no reason to admit them over likelihood statements. In ruling on objections to traditional source attributions buttressed by the many calls for evidence-centric presentations, courts would be remiss to think that Rule 704 favors either school of thought.

Important quote:
... Thus far, I have assumed that all source attributions are ultimate opinions as those words are used in Rule 704. The rule applies to any opinion from any witness—expert or lay—that  “embraces an ultimate issue.” But the identity of the source of a trace is not necessarily an ultimate issue. The conclusion that the print lifted from a gun comes from a specific finger does not identify the murder defendant is the one who pulled the trigger. The examiner’s source attribution bears on the ultimate issue of causing the death of a human being, but the examiner who reports that the prints were defendant's is not opining that the defendant not only touched the gun (or had prints planted on it) but also pulled the trigger. Indeed, the latent print examiner would have no scientific basis for such an opinion on an element of the crime of murder..."

Download the full article here.

Have a great day, my friends.

Keywords: evidence, forensic science, identification, expert opinions, ultimate issues, Rule 704, likelihoods, individualization, probability