A Caltech Library Service

In Defense of Unanimous Jury Verdicts: Communication, Mistrials, and Sincerity

Coughlan, Peter J. (1997) In Defense of Unanimous Jury Verdicts: Communication, Mistrials, and Sincerity. Social Science Working Paper, 1012. California Institute of Technology , Pasadena, CA. (Unpublished)

[img] PDF (sswp 1012 -Nov. 1997) - Submitted Version
See Usage Policy.


Use this Persistent URL to link to this item:


It is a widely held belief among legal theorists that the requirement of unanimous jury verdicts in criminal trials reduces the likelihood of convicting an innocent defendant. This belief is, to a large extent, dependent upon the assumption that all jurors will vote sincerely based on their own impression of the trial evidence. Recent literature, however, has drawn this assumption into question, and simple models of jury procedure have been constructed in which, except under very strict conditions, it is never a Nash equilibrium for all jurors to vote sincerely. Moreover, Nash equilibrium behavior in these models leads to higher probabilities of both convicting an innocent defendant and acquitting a guilty defendant under unanimity rule than under a wide variety of alternative voting rules, including simple majority rule. The present paper extends these models by adding minimal enhancements that we argue bring the existing models closer to actual jury procedures. In particular, we separately analyze the implications of (1) incorporating the possibility of mistrial and (2) allowing limited communication among jurors. Under each of these enhancements, we identify general conditions under which sincere voting is, in fact, a Nash equilibrium. We further demonstrate that under such sincere voting equilibria, unanimous jury verdicts perform better than any alternative voting rule in terms of minimizing probability of trial error and maximizing expected utility.

Item Type:Report or Paper (Working Paper)
Additional Information:Revised version. Original dated to August 1997. The comments and suggestions of Tom Palfrey, Richard McKelvey, Jeffrey Banks and Tim Feddersen are greatly appreciated. I would also like to thank John Ledyard, Kim Border, Paolo Ghirardato, Simon Wilkie, Jonathon Katz, Anthony Kwasnica, Roberto Weber, Tara Butterfield, John Patty, and Garrett Glasgow for their observations and suggestions during preliminary presentations at CalTech.
Group:Social Science Working Papers
Series Name:Social Science Working Paper
Issue or Number:1012
Record Number:CaltechAUTHORS:20170814-143254954
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:80374
Deposited By: Jacquelyn Bussone
Deposited On:15 Aug 2017 16:52
Last Modified:03 Oct 2019 18:30

Repository Staff Only: item control page