Do Jurors Give Appropriate Weight to Forensic Identification Evidence?

39 Pages Posted: 20 Apr 2013

See all articles by William C. Thompson

William C. Thompson

University of California, Irvine - Department of Criminology, Law and Society

Suzanne O. Kaasa

Northrop Grumman Technical Services/Defense Personnel Security Research Center

Tiamoyo Peterson

University of California, Irvine - Department of Psychology and Social Behavior

Multiple version iconThere are 2 versions of this paper

Date Written: June 2013

Abstract

Do jurors give appropriate weight to forensic identification evidence? When judging the value of forensic evidence, are they sensitive to the probability of a false match? To answer these questions, we conducted two jury simulation experiments - the first with undergraduate participants, the second with members of a county jury pool. The experiments examined the weight that participants gave to forensic DNA evidence relative to Bayesian norms when evaluating a hypothetical criminal case. We found that aggregate judgments were generally consistent with Bayesian expectations, although people overvalued the DNA evidence when the probability of a false report of a match was high relative to the random match probability. Judgments of the chances the defendant was guilty varied appropriately in response to the variation in the probability of a false report of a match, as did verdicts. Our findings refute claims that jurors are always conservative Bayesians when evaluating forensic evidence and suggest, instead, that they use a variety of judgmental strategies and sometimes engage in fallacious statistical reasoning. In light of these findings, we identify circumstances in which forensic evidence may be overutilized, discuss implications for legal policy, and suggest additional lines of research.

Suggested Citation

Thompson, William C. and Kaasa, Suzanne O. and Peterson, Tiamoyo, Do Jurors Give Appropriate Weight to Forensic Identification Evidence? (June 2013). Journal of Empirical Legal Studies, Vol. 10, Issue 2, pp. 359-397, 2013. Available at SSRN: https://ssrn.com/abstract=2254203 or http://dx.doi.org/10.1111/jels.12013

William C. Thompson (Contact Author)

University of California, Irvine - Department of Criminology, Law and Society ( email )

Irvine, CA
United States

Suzanne O. Kaasa

Northrop Grumman Technical Services/Defense Personnel Security Research Center ( email )

Defense Personnel Security Research Center
20 Ryan Ranch Road
Monterey, CA 93940
United States

Tiamoyo Peterson

University of California, Irvine - Department of Psychology and Social Behavior ( email )

4201 Social & Behavioral Sciences Gateway
University of California, Irvine
Irvine, CA 92697-7085
United States

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