THE EMPIRICAL EVIDENCE IN THIS STUDY CAME FROM TWO SOURCES. FIRST, INFORMATION ABOUT THE EFFECTS OF THE UNANIMITY REQUIREMENT ON VERDICTS AND THE RELATIONSHIP BETWEEN INDIVIDUAL PREDELIBERATION VOTES AND FINAL GROUP VERDICTS CAME FROM ACTUAL COURT CASES. A SECOND SOURCE OF EMPIRICAL EVIDENCE WAS A SERIES OF JURY SIMULATION STUDIES CONDUCTED BY SOCIAL SCIENTISTS. THE BASIC PARADIGM EMPLOYED IN THIS RESEARCH WAS THE PRESENTATION OF THE SAME CRIMINAL CASE TO DIFFERENT GROUPS OF SUBJECTS. THESE GROUPS OF SUBJECTS HAD TO DELIBERATE ON THE CASE UNTIL A GROUP VERDICT WAS REACHED. HALF THE GROUPS WERE TOLD THEY HAD TO REACH A UNANIMOUS GROUP DEICISON; THE OTHER HALF WERE TOLD THAT THEY MUST REACH A MAJORITY DECISION. THE EXPERIMENTER THEN COMPARED THE VERDICTS AND DELIBERATIONS TO DETERMINE THE EFFECTS OF THE UNANIMITY REQUIREMENT. STUDIES INDICATE THAT MAJORITY JURIES DEVOTE LESS TIME TO THE TASK AT HAND AND PAY LESS ATTENTION TO MEMBERS ARGUING MINORITY VIEWPOINTS THAN UNANIMITY JURIES. MINORITY MEMBERS IN MAJORITY JURIES TALK LESS AND REPORT MORE FREQUENTLY THAT THEY WERE UNABLE TO MAKE ALL OF THEIR ARGUMENTS THAN DO MINORITY MEMBERS OF UNANIMITY JURIES. ALTHOUGH THERE CAN BE NO DIFFERENCES IN THE CONVICTION-ACQUITTAL RATIOS OF VERDICTS RENDERED BY UNANIMITY AND MAJORITY JURIES, THESE GROUP-PROCESS DIFFERENCES MAY CONTRIBUTE TO A LOWERING OF THE RELIABILITY OF JURY VERDICTS UNDER MAJORITY DECISION RULE. EMPIRICAL EVIDENCE SUPPORTS THE IDEA THAT UNANIMOUS DECISIONS ARE USUALLY 'MAJORITY RULE' DECISIONS. HOWEVER, THERE MAY BE IMPACT EXCEPTIONS TO THIS MAJORITY RULE WHICH MERIT THE CONTINUED REQUIREMENT FOR UNANIMITY IN DELIBERATIONS. THESE ISSUES AND THEIR EMPIRICAL EVIDENCE SHOULD BE CONSIDERED IN MAKING POLICY DECISIONS CONCERNING THE UNANIMITY REQUIREMENT. REFERENCES AND AN APPENDIX ARE PROVIDED IN THE PAPER. (AUTHOR ABSTRACT MODIFIED--LWM)