Strategic Voting in a Jury Trial with Plea Bargaining

Abstract

We study the criminal court process focusing on the interaction between plea bargaining and jury trials. We model plea bargaining such that a prosecutor makes a take-it-or-leave-it offer and a defendant, who is either guilty or innocent, pleads either guilty or not guilty. If the defendant pleads not guilty, the case goes to a jury trial, which follows a strategic voting model. Plea bargaining produces a bias in which the defendant is less likely to be guilty if the case goes to trial, which in turn alters the jurors' voting behavior. Conversely, anticipated jury trial outcomes affect a prosecutor and a defendant while they participate in a plea bargain. We find that the equilibrium behavior in a court with plea bargaining and a jury trial, resembles the equilibrium behavior in the separate jury model, though jurors may act as if they echo the prosecutor's preference against convicting the innocent and acquitting the guilty. We also compare two voting paradigms, unanimity and non-unanimity. The unanimity rule is inferior to non-unanimity because the ex-ante punishment delivered to the innocent or undelivered to the guilty by unanimity rule does not vanish as the size of jury gets large.

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