Does Psychopathy Influence Juror Decision-Making in Capital Murder Trials? "The Devil is in the (Methodological) Details"

Concerns about the potentially stigmatizing impact of psychopathy evidence in court have been expressed for decades. Saks et al. manipulated diagnostic information (e.g., psychopathy, schizophrenia) and the basis for that evidence (e.g., clinical, neuroimaging) to examine effects on outcomes in two capital murder case vignettes. Somewhat surprisingly, their psychopathy manipulation did not have a consistently adverse impact on juror attitudes relative to other diagnoses or a control condition. We administered the Saks et al. stimulus materials to college students (N = 569), but added a scale quantifying participant ratings of how psychopathic they perceived the defendant to be. Notably, we obtained uniformly high mean psychopathy ratings across all study conditions. In addition, participants who rated the defendant as more psychopathic (regardless of condition) were more likely to support death verdicts. We discuss the implications of our results in terms of the design of experimental manipulations of mental health evidence for jury simulations.