Thus Hare's Psychopathic Checklist—Revised (PCL-R) has come to be the gold standard for making the diagnosis of psychopathy, both in the general population and in prison settings. Because this assessment tool is so important, a brief description of it is warranted. The PCL-R is a 20-item checklist—or, more accurately, a 20-item clinical-construct rating scale—completed on the basis of a semistructured interview and detailed collaboration or file information. Each item is scored as 0, 1, or 2, yielding a maximum possible score of 40. The mean PCL-R scores in North American populations of male and female offenders typically range from 22 to 24, with standard deviations of 6 to 8. Mean scores in North American forensic psychiatric populations are somewhat lower, around 20. For research purposes, a score of 30 is generally considered indicative of psychopathy. The PCL-R now has a shortened version, called the Psychopathic Checklist: Screening Version, that also appears to be valid and reliable in identifying this disorder.