The Effect of Psychopathy Trait Descriptions on Mock Juror Decision-Making

Layperson juror interpretation of mental health evidence, such as psychopathy, can be key in deciding death penalty cases. The present experimental study examined how case vignettes that included descriptions of distinct facets of psychopathic traits (i.e., criterion effects) differentially influenced juror decision-making across proximal judgements (e.g., perceived treatment amenability) medial judgements (future dangerousness and treatment amenability) and distal judgements (e.g., sentencing to death). Undergraduate student participants (N=444) read one of five vignettes describing interpersonal-affective traits, antisocial-lifestyle psychopathic traits, both sets of traits, high-functioning autistic traits, or mixed-desirability control (non-clinical) traits and then made sentencing decisions. We found that psychopathy trait descriptions, particularly interpersonal-affective traits, and perceived psychopathy of the defendant were significantly related to mock juror ratings of lower treatment amenability and higher future dangerousness but were not related to sentencing. Instead, mock juror gender and judgements of defendant treatment amenability and future dangerousness predicted sentencing decision. These mixed results suggest nuance in juror decision-making that should be further examined by investigating potential moderators. Understanding juror perceptions of mental health conditions is key to preventing bias in the courtroom.