Jury size and the Hung-Jury paradox

In Williams v. Florida (399 U.S. 78 [1970]), the U.S. Supreme Court decided a case addressing the constitutionality of juries composed of fewer than 12 jurors, ruling that smaller juries are not inconsistent with the Sixth Amendment. In an effort to speed deliberation and reduce the rate of mistrials, 11 states have subsequently adopted juries of fewer than 12 in state felony trials, and 40 states have diminished their jury sizes for state misdemeanor trials. Curiously, however, contrary to the predictions of probability theory and common sense, these reductions in jury sizes have failed to deliver the expected reduction in mistrial rates. In this paper, we offer two interrelated explanations for this fact: informational cascades and the heterogeneity of jurors.