Differential effects of jury size on verdicts following deliberation as a function of the apparent guilt of a defendant.

The United States Supreme Court ruled in the case of Williams vs Florida (1970) that a Florida statute providing for 6-member juries was constitutional. Allowing the relevance of empirical studies concerning differential effects of jury size, the Court concluded that existing evidence was insufficient to demonstrate that the verdicts of 6-member juries would be different from those of 12-member juries or would operate to the disadvantage of a defendant. Given the paucity of relevant data supportive of such differences, the Court decided in favor of allowing the smaller juries. The present study was designed to determine experimentally whether the 6-member jury was more or less advantageous to the defendant than a 12-member jury at each of 2 levels of apparent guilt of the defendant. Ss were 360 undergraduates. Consistent with predictions based upon logical considerations and upon small group research, jury size had no effect upon conviction when apparent guilt was low (only 2 out of 10 juries of each size reached a guilty verdict), but when apparent guilt was high, 6-member juries were substantially more likely to convict (9 out of 10) than were 12-member juries (2 out of 10; (p < .001). (22 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved)

[1]  F. Strodtbeck,et al.  Social Status in Jury Deliberations , 1957 .

[2]  J. H. Davis.  Group decision and social interaction: A theory of social decision schemes. , 1973 .

[3]  A. Hare.  A Study of Interaction and Consensus in Different Sized Groups , 1952 .

[4]  J. Thibaut,et al.  Order of Presentation at Trial , 1972 .

[5]  John Thibaut,et al.  Adversary Presentation and Bias in Legal Decisionmaking , 1972 .

[6]  A. Hare,et al.  Handbook of small group research , 1962 .

[7]  H. Zeisel.  The Waning of the American Jury , 1972 .

[8]  Hugo Münsterberg,et al.  On the Witness Stand , 1908 .

[9]  Sutcliffe Jp,et al.  A general method of analysis of frequency data for multiple classification designs. , 1957 .

[10]  Dale W. Broeder.  The University of Chicago Jury Project , 1959 .

[11]  B. J. Winer.  Statistical Principles in Experimental Design , 1992 .

[12]  Herbert Friedman,et al.  Trial by Jury: Criteria for Convictions, Jury Size and Type I and Type II Errors , 1972 .

[13]  H. Zeisel,et al.  The American Jury , 1966 .

[14]  S. Asch.  Effects of Group Pressure Upon the Modification and Distortion of Judgments , 1951 .

[15]  Forrest W. Young,et al.  Interactive scaling with individual subjects , 1972 .

[16]  R. Bales,et al.  Personality and Interpersonal Behavior. , 1971 .

[17]  Robert I. Gordon,et al.  A study in forensic psychology : petit jury verdicts as a function of the number of jury members , 1968 .

[18]  Robert W. Holt,et al.  The decision processes of 6- and 12-person mock juries assigned unanimous and two-thirds majority rules. , 1975 .

[19]  Harry Kalven,et al.  The American Jury , 1967 .