How reliable are Psychopathy Checklist-Revised scores in Canadian criminal trials? A case law review.

The Psychopathy Checklist-Revised (PCL-R; Hare, 2003) is a professional rating scale that enjoys widespread use in forensic and correctional settings, primarily as a tool to inform risk assessments in a variety of types of cases (e.g., parole determinations, sexually violent predator [SVP] civil commitment). Although widely described as "reliable and valid" in research reports, several recent field studies have suggested that PCL-R scores provided by examiners in forensic cases are significantly less reliable than the interrater reliability values reported in research studies. Most of these field studies, however, have had small samples and only examined SVP civil commitment cases. This study builds on existing research by examining the reliability of PCL-R scores provided by forensic examiners in a much more extensive sample of Canadian criminal cases. Using the LexisNexis database, we identified 102 cases in which at least 2 scores were reported (of 257 total PCL-R scores). The single-rater intraclass correlation coefficient (ICC(A1)) was .59, indicating that a large percentage of the variance in individual scores was attributable to some form of error. ICC values were somewhat higher for sexual offending cases (.66) than they were for nonsexual offending cases (.46), indicating that poor interrater reliability was not restricted specifically to the assessment of sexual offenders. These and earlier findings concerning field reliability in legal cases suggest that the standard error of measurement for PCL-R scores that are provided to the courts is likely to be much larger than the value of 2.90 reported in the instrument's manual.