Interactions between jurors as a function of majority vs. unanimity decision rules

Nemeth, C. (1977). Interactions between jurors as a function of majority vs. unanimity decision rules. Journal of Applied Social Psychology, 7, 38-56.

Ruling on the constitutionality of less than unanimous juries, the majority and dissenting Justices of the Supreme Court offered differing theories of social influence processes in jury deliberations. Some areas of disagreement involved verdict distribution, majority-minority interactions, and community confidence as a function of unanimity vs. non-unanimity requirements. The present series of three studies concentrated on these issues. In the first two studies, groups that were split 4:2 in initial vote deliberated a case involving first degree murder. In the third study, individuals served as jurors in each of seven mock trials (both civil and criminal). Half of these groups were required to deliberate to unanimity, the other half being required to deliberate to 2/3 majority. Results indicated that verdicts were not appreciably altered as a result of unanimity vs. non-unanimity requirements. However, unanimity groups were more likely to reach full consensus; their deliberations were characterized by more “conflict”; more opinions were changed as a result of the deliberation process; they reported more confidence in the verdict and tended to feel that justice had been administered. The findings tend to corroborate the influence theories of the dissenting Justices. Strong majority effect; 2/3 majorities favoring not guilty much more successful than those favoring conviction. Juries with unanimity requirement more likely to hang and took longer to deliberate when majority favored guilt. Deliberation characterized by more affect, disagreement, and information sharing under unanimity rule. <2>No significant differences on verdict or deliberation time as a function of decision rule.

http://onlinelibrary.wiley.com/doi/10.1111/j.1559-1816.1977.tb02416.x/abstract