Controversy surrounds the use of the Hare Psychopathy Checklist—Revised (Hare, 1991, 2003) in capital murder cases, where it has been introduced to support prosecution claims that a defendant represents a “continuing threat to society”. Although widely presumed to have a prejudicial impact (e.g., American Psychological Association, 2004), little is known about how the lay public reacts to data derived from ostensibly stigmatizing assessment instruments such as the PCL-R. The present study examined the effect of psychopathy data on layperson attitudes by having 203 undergraduates review a capital murder case where the results of the defendant's psychological evaluation were experimentally manipulated. When expert testimony described the defendant as psychopathic, a much larger percentage of participants supported a death sentence (60%) than when testimony indicated that he was psychotic (30%) or not mentally disordered (38%). Interestingly, participant ratings of how psychopathic they perceived the defendant to be—regardless of the testimony condition to which they had been assigned—also predicted support for a death sentence. Given the limited probative value of the PCL-R in capital cases and the prejudicial nature of the effects noted in this study, we recommend that forensic examiners avoid using it in these trials. Copyright © 2005 John Wiley & Sons, Ltd.