Juror Certainty about Firearms Evidence: Examination Effects

Cooper, Sarah Lucy and Scanlon, Paraic and Shooter, Amelia (2024) Juror Certainty about Firearms Evidence: Examination Effects. Criminal Law Practitioner. (In Press)

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Firearms examiners routinely compare tool-marks on suspect ammunition with those on ammunition test-fired by a suspect weapon to evaluate if they can be associated. The discipline has been subject to criticism, including by the National Academy of Sciences, but the testimony of firearms examiners is routinely admitted as expert evidence in the United States (US). Jurors must determine the weight of expert evidence, which opposing and proffering lawyers can aim to, respectively, discredit on cross-examination and rehabilitate on redirect-examination. The authors investigated the effect of both cross and redirect- examination on potential US jurors’ certainty about expert firearms evidence using a series of
online vignettes. Participants (n=114) were asked to rate their certainty (on a scale of 0-100) about three expert statements – Very Certain (an exact match), Certain (a match to a reasonable degree of certainty), and Uncertain (evidence is unsuitable for comparison) – when assigned to one of three conditions. These conditions were a judicial instruction about weighing the evidence (control condition); a cross-examination referencing criticism of firearms evidence; and a redirect-examination (following the cross-examination) referencing the routine admission of firearms evidence. Analysis was undertaken both between groups and between the statements given to each group. Results suggest that experts conveying high certainty create higher certainty in jurors, cross-examination has a detrimental effect on this certainty, but redirect-examination does not reduce this detrimental effect.

Item Type: Article
19 June 2024Accepted
Subjects: CAH04 - psychology > CAH04-01 - psychology > CAH04-01-05 - others in psychology
CAH16 - law > CAH16-01 - law > CAH16-01-01 - law
Divisions: Faculty of Business, Law and Social Sciences > College of Law, Social and Criminal Justice
Faculty of Business, Law and Social Sciences > College of Psychology
Depositing User: Sarah Cooper
Date Deposited: 25 Jun 2024 14:16
Last Modified: 25 Jun 2024 14:21
URI: https://www.open-access.bcu.ac.uk/id/eprint/15579

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