The effects of jury size and polling method on the process and product of jury deliberation.

612 undergraduates in 15 same-sex groups of 3, 6, or 12 Ss participated in mock jury deliberations over 9 armed robbery cases, and both individual and group verdicts were obtained, to test the predictions that larger juries would hang more often, particularly for close cases, and that secret polling would lead to fewer hung juries than open polling. It is asserted that failures to confirm these predictions in previous studies were probably due to inadequate sample sizes or to insufficiently close cases; the present study minimized these problems. Social decision scheme and social transition scheme analyses permitted comparisons of the decision-making processes of the different-sized mock juries, and jury groups used either secret written ballots or a show of hands for polling. Results show that, as group size increased, the observed probability of a hung jury significantly increased. No process differences between 6- and 12-person groups were detected, but 3-person groups exhibited several process differences in comparison to both larger groups. When cases were close, the likelihood of a hung jury for typically sized juries was found to be lower when the group was polled by secret ballot than when a show-of-hands was used.