Actuarial risk assessment and recidivism in a sample of UK intellectually disabled sexual offenders

Abstract

This study examines the effectiveness of three risk assessment instruments: Static-99, Risk Matrix 2000 (RM2000) and the Rapid Risk of Sex Offender Recidivism (RRASOR), in predicting sexual recidivism among 27 intellectually disabled sex offenders. The overall sexual offence reconviction rate was 30%, while non-recidivists remained offence-free over 76 months of follow-up. Static-99 presented as performing as well as guided clinical judgements in mainstream population studies area under the curve (AUC)=0.64] exceeding the performance of RM2000 (AUC=0.58) in predicting sexual recidivism. However, the results were not statistically significant. In contrast to previous findings, the RRASOR presented the worst level of prediction (AUC=0.42). These results highlight the need to investigate further with larger sample sizes and in conjunction with more dynamic measures of risk. Proposed relevant factors are discussed in detail.