Assessing the Validity of the Revised Psychopathy Checklist for Use with Insanity Acquittees

The present study used item response theory (IRT) methods to assess the validity of the Psychopathy Checklist-Revised (PCL-R; Hare, 2003) for use with men and women who have been found not guilty by reason of insanity (NGRI). Though the validity of the PCL-R has been studied in many contexts, relatively little is known about the test\u27s psychometric properties in instances when it is used to evaluate NGRI acquittees, and female NGRI acquittees in particular. IRT was used to (a) detect and quantify differential item functioning (DIF) on the PCL-R between men and women, and (b) examine qualitative differences in the construct of psychopathy between the present NGRI sample and the PCL-R\u27s normative sample. The present sample was comprised of approximately 250 male and female NGRI acquittees. Results showed that the PCL-R assigned higher scores to females than it did to males with comparable levels of psychopathy. This was due to the impact of DIF on several of the test\u27s items. Additionally, results showed that the construct of psychopathy, as operationalized by the PCL-R, functioned similarly for NGRI acquittees as it did for other populations described in the literature, including the PCL-R\u27s normative sample. Specifically, the interpersonal and affective aspects of psychopathy were more central to the construct than the lifestyle or antisocial aspects. Implications for theory, research, and practice are discussed as well as directions for future research