Campus Units

Center for Statistics and Applications in Forensic Evidence (CSAFE)"

Document Type

Article

Publication Version

Accepted Manuscript

Publication Date

2020

Journal or Book Title

Law & Human Behavior

Volume

44

Issue

5

First Page

412

Last Page

423

DOI

10.1037/lhb0000423

Abstract

Objectives: 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). Hypotheses: Four hypotheses were tested. First, jurors will accord significant weight to firearm testimony that declares a “match” compared to testimony that does not (Experiments 1 and 2). Second, variations to “match” language will not affect guilty verdicts (Experiment 1). Third, only the most cautious language (“cannot exclude the gun”) would lower guilty verdicts (Experiment 1). Fourth, cross-examination will reduce guilty verdicts depending on specific language used (Experiment 2). Method: In two preregistered, high-powered experiments with 200 mock jurors per cell, participants recruited from Qualtrics Panels were presented with a criminal case containing firearms evidence, which varied the wording of the examiner’s conclusion and whether cross-examination was present. These variations include conclusion language used by practitioners, language advised by government organizations, and language required by judges in several cases. Participants gave a verdict, rated the evidence and expert in all conditions. Results: Guilty verdicts significantly increased when a match was declared compared to when a match was not declared. Variation in conclusion language did not affect guilty verdicts nor did it affect jurors’ estimates of the likelihood the defendant’s gun fired the bullet recovered at the crime scene. In contrast, however, a more cautious conclusion that an examiner “cannot exclude the defendant’s gun” did significantly reduce guilty verdicts and likelihood estimates alike. The presence of cross-examination did not affect these findings. Conclusion: 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.

Comments

This article is published as Garrett, B. L., Scurich, N., & Crozier, W. E. (2020). Mock jurors’ evaluation of firearm examiner testimony. Law and Human Behavior, 44(5), 412–423. https://doi.org/10.1037/lhb0000423. Posted with permission of CSAFE.

Copyright Owner

APA

Language

en

File Format

application/pdf

Published Version

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