The Use of Psychopathy Assessments in Canadian Case Law: A Quantitative and Qualitative Survey of Court Records from 1980-2023

This study investigated the use of psychopathy assessments in Canadian courts between 1980 and 2023. We reviewed 3,315 court cases and found that psychopathy assessments are used in two distinct ways, either as a clinical measure of psychopathy or exclusively for risk assessment purposes. Psychopathy assessments are most commonly introduced in court by prosecutors, with the Hare Psychopathy Checklist–Revised (PCL-R) being the most frequently used tool. The use of psychopathy assessments increased 958% from the year 2000 to its peak in 2013, followed by a 10-year gradual (63%) decline. There was evidence of adversarial allegiance where prosecution-retained experts gave defendants higher PCL-R scores (d = 1.08) compared to defense-retained experts. PCL-R assessments showed poor reliability when comparing paired scores between prosecution and defense experts, suggesting high risk of Type 1 and 2 errors. Intraclass correlation coefficient (ICC2,1) between prosecution- and defense-retained experts was .079 (95% CI [-0.12, 0.34]), where 40% of experts had a ≥5.9 points scoring difference. A qualitative analysis of 183 expert testimonies on the perceived forensic risk and treatment prospects associated with psychopathy showed significant variability in expert testimonies. Most experts linked psychopathy to high risk of recidivism (72.36%) and described it as a categorically untreatable condition (50.63%), where many experts also stated that treatment makes psychopathic persons worse (15.82%). These findings suggest that some expert testimonies on psychopathy are not aligned with the empirical research. We discuss the potential implications for legal practitioners and comment on the future role of psychopathy assessments in Canadian courts.