Abstract

http://ssrn.com/abstract=2214442
 


 



Do Jurors Give Appropriate Weight to Forensic Identification Evidence?


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

February 9, 2013

Journal of Empirical Legal Studies, Forthcoming
UC Irvine School of Law Research Paper No. 2013-124

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 over-valued 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 over-utilized, discuss implications for legal policy, and suggest additional lines of research.

Number of Pages in PDF File: 67

Keywords: forensic science, jury, DNA, statistic, evidence, Bayes, probability, decision making, judgment

JEL Classification: C11, C44, C91, C92, K14, K41

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Date posted: February 10, 2013 ; Last revised: July 25, 2013

Suggested Citation

Thompson, William C. and Kaasa, Suzanne O. and Peterson, Tiamoyo, Do Jurors Give Appropriate Weight to Forensic Identification Evidence? (February 9, 2013). Journal of Empirical Legal Studies, Forthcoming; UC Irvine School of Law Research Paper No. 2013-124. Available at SSRN: http://ssrn.com/abstract=2214442

Contact Information

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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