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Mock Juror Perceptions of Forensics

This CSAFE Center Wide webinar was presented on December 8, 2020 by:

Brandon Garrett – L. Neil Williams Professor of Law, Faculty Director at the Wilson Center for Science and Justice

Nicholas Scurich – Associate Professor of Criminology, Law & Society, Vice Chair of the Department of Psychological Science at the University of California, Irvine

William Crozier – Research Director of the Wilson Center for Science and Justice

The presenters have provided a copy of the paper discussed.

Presentation Description:

We will describe two recent experiments.  In the first, we conducted two studies whether knowledge of an expert’s performance on blind proficiency testing affects trust in the expert witness, the evidence (fingerprint or bitemark), and verdicts.  We also examined whether cross-examination affected these outcomes.  As labs consider adopting blind proficiency testing programs, we wanted to better understand how information about those programs impacts jurors.  Our results support the view that additional blind proficiency testing programs, in addition to their quality control benefits, do not prejudice jurors.
Second, firearms experts traditionally have testified that a weapon leaves “unique” toolmarks, so bullets or cartridge casings can be visually examined and conclusively matched to a particular firearm. Recently, due to scientific critiques, Department of Justice policy, and judges’ rulings, firearms experts have tempered their conclusions. In two experiments, we tested whether this ostensibly more cautious language has its intended effect on jurors (Experiment 1), and whether cross-examination impacts jurors’ perception of firearm testimony (Experiment 2). We found that apart from the most limited language (“cannot exclude the defendant’s gun”), judicial intervention to limit firearms conclusion language is not likely to produce its intended effect. Moreover, cross-examination does not appear to affect perceptions or individual juror verdicts.

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