Does interrater (dis)agreement on Psychopathy Checklist scores in sexually violent predator trials suggest partisan allegiance in forensic evaluations?

Many studies reveal strong interrater agreement for Hare's Psychopathy Checklist-Revised (PCL-R) when used by trained raters in research contexts. However, no systematic research has examined agreement between PCL-R scores from independent clinicians who are retained by opposing sides in adversarial legal proceedings. We reviewed all 43 sexual-offender civil-commitment trials in one state and identified 23 cases in which opposing evaluators reported PCL-R total scores for the same individual. Differences between scores from opposing evaluators were usually in a direction that supported the party who retained their services. These score differences were greater in size than would be expected based on the instrument's standard error of measurement or the rater agreement values reported in previous PCL-R research. The intraclass correlation for absolute agreement for the PCL-R Total score from a single rater (ICC 1,A = .39) was well below levels of agreement observed for the PCL-R in research contexts, and below published test-retest values for the PCL-R. Results raise concerns about the potential for a forensic evaluator's "partisan allegiance" to influence PCL-R scores in adversarial proceedings.