The preassessment level of moral reasoning as determined by Rest's Defining Issues Test was of primary importance. Sixty-six subjects, selected from approximately 200 student volunteers from introductory psychology classes were used in Experiment 1. Subjects were divided into three types of six-member juries and shown a 10-minute videotaped simulated trail of a young white male accused of assault and battery against a police officer. In Experiment 2, 105 undergraduate psychology students were given a Law and Order Questionnaire to assess attitudes toward mechanics and police officers as occupational groups. Experiment 3 explored the effects of manipulating the moral level of closing appeals of attorneys, and Experiment 4 used 131 general psychology students to clarify the effects of attorneys' closing arguments on jurors and their votes. Results of Experiments 1 and 3 indicate that principled moral reasoners favored acquittal more than conventional moral reasoners. Experiment 2 suggested that dispositional bias was related to moral reasoning processes and not to other attitudinal dispositions. Experiments 3 and 4 reflected combinations of conventional and postconventional reasoning. All four experiments contributed to the understanding of relationships among decisionmakers' personal characteristics, situational demands, and behavioral outcomes by examining these variables in the context of a jury trial. Tabular data and 13 references.