A Comparison of the Predictive Properties of Nine Sex Offender Risk Assessment Instruments

Sex offender treatment is most effective when tailored to risk-need-responsivity principles, which dictate that treatment levels should match risk levels as assessed by structured risk assessment instruments. The predictive properties, missing values, and interrater agreement of the scores of 9 structured risk assessment instruments were compared in a national sample of 397 Dutch convicted sex offenders. The instruments included the Rapid Risk Assessment for Sexual Offense Recidivism, Static-99, Static-99R, a slightly modified version of Static-2002 and Static-2002R, Structured Anchored Clinical Judgments Minimum, Risk Matrix 2000, Sexual Violence Risk 20, and a modified version of the Sex Offender Risk Appraisal Guide; sexual and violent (including sexual) recidivism was assessed over 5-and 10-year fixed and variable follow-up periods. In general, the instrument scores showed moderate to large predictive accuracy for the occurrence of reoffending and the number of reoffenses in this sample. Predictive accuracy regarding latency showed more variability across instrument scores. Static-2002R and Static-99R scores showed a slight but consistent advantage in predictive properties over the other instrument scores across outcome measures and follow-up periods in this sample. The results of Sexual Violence Risk 20 and Rapid Risk Assessment for Sexual Offense Recidivism scores were the least positive. A positive association between predictive accuracy and interrater agreement at the item level was found for both sexual recidivism (r = .28, p = .01) and violent (including sexual) recidivism (r = .45, p < .001); no significant association was found between predictive accuracy and missing values at the item level. Results underscore the feasibility and utility of these instruments for informing treatment selection according to the risk-need-responsivity principles.