Defendant mental illness and juror decision-making: A comparison of sample types

Two studies were conducted with separate student and community samples to explore the effect of sample types and the influence of defendant mental illness on juror decision-making. Following the completion of a pre-trial questionnaire in which jurors’ attitudes towards mental illness were assessed, participants were provided with a robbery trial transcript, wherein the mental illness of the defendant was manipulated. Participants then answered a questionnaire to assess their knowledge of the scenario, their verdict, verdict confidence, and sentencing decision. Limited relationships were found between the variables in both Study 1 and Study 2. Neither attitude ratings nor mental illness type had a significant effect on juror decisions. Samples differed in terms of the paths through which juror decisions were achieved. Findings suggest that sample type may be particularly relevant for this topic of study, and that future research is required on legal proceedings for cases involving a defendant with a mental illness.