Foss, R. D. (1981). Structural effects in simulated jury decision making. Journal of Personality and Social Psychology, 40, 1055-1062.
Studied 28 12-person (17–56 yr old undergraduates) simulated juries to examine the effects of (a) a formally imposed decision rule (unanimity vs quorum) and (b) initial within-jury verdict preference distributions on group deliberation processes and decisions. Behavioral indicators were used to monitor the nature of group process under differing structural requirements while groups discussed either a more or a less ambiguous case. Compared with juries required to reach unanimity, juries required to obtain a quorum of 10 reached decisions twice as quickly and were much less likely to come to a stalemate resulting in a hung jury. Most important, these differences were due to the development of a different process from that which developed when juries were required to reach unanimity.
Juries operating under 5/6 decision rule twice as fast and much less likely to hang than unanimous juries; no impact of decision rule on verdicts. Juries exposed to low-ambiguity evidence convicted more and hung less.