The optimal jury size when jury deliberation follows a random walk.

The existing literature does not agree on the optimal jury size. We demonstrate that the probability of type I and type II errors is not sensitive to the number of jurors under the following three conditions: jurors receive independent signals about a defendant’s guilt during the evidence stage of the trial; the jurors truthfully reveal their signals before deliberations begin through their votes on the first ballot; and the jury’s deliberation follows a random walk. Since the opportunity cost of jury service is positive, this implies an optimal jury size of one. [ABSTRACT FROM AUTHOR]