The subjects were 232 college students who were questioned individually and found to be willing to impose the death penalty. Each juror read a description of 1 to 12 simulated trials involving the death penalty and completed a questionnaire indicating both their penalty decision and the reasons for it. Each trial involved one of three capital crimes and one of four defense strategies. The three crimes were robbery with anunplanned murder, a robbery with wanton violence and a murder, and a multiple murder. The four possible defenses were a defense based on opposition to capital punishment in general, a defense based on the offender's social history, a mental illness defense, and no defense. Jurors could vote for the death penalty or life imprisonment with no parole. Jurors were least punitive for the robbery-murders and most punitive toward the multiple murderers. The most effective defense was a conceptual argument against capital punishment. The mental illness defense was the least effective. Three attributional variables mediated the penalty decisions: (1) juror perceptions of the defendant's volition, (2) juror perceptions of the defendant's future dangerousness, and (3) juror perceptions of the relative competence of the opposing attorneys. Tables, figures, footnotes, and 17 references. (Author abstract modified)