Reliability and validity of the Static-99R in sex offenders with intellectual disabilities

Abstract

Purpose Risk assessment studies involving recidivism in sex offenders with intellectual disabilities (SOIDs) continue to be scarce, limited and producing mixed results. This study aims (to test the ability ...) to test the ability of one such instrument (the Static-99R) to predict intramural sexual and violent incidents involving members of this group. Design/methodology/approach The Static-99R was prospectively scored for 38 SOIDs. Occurrences of any violent or sexual incident and/or illegal sexual behaviour were recorded during a minimum period of six months. Predictive accuracy was analysed using several performance indicators. Findings The Static-99R significantly predicted sexual incidents (area under the curve = 0.70) but failed to predict violent and illegal sexual incidents. Regarding illegal sexual incidents, the instrument was better at detecting low-risk individuals than high-risk offenders. Originality/value Risk assessment studies, both in offenders with and without an intellectual disability (ID), rarely use multiple accuracy estimates. The current study used both discrimination and calibration indicators to evaluate the ability of the Static-99R to detect low- and high-risk offenders.