Sex offender risk assessment with the Risk Matrix 2000: validation and guidelines for combining with the STABLE-2007

Comprehensive risk assessment can benefit from combining static and dynamic scales. The purpose of this study was to validate the Risk Matrix 2000, examine incremental validity of the STABLE-2007 and develop structured rules for combining the two scales. In a routine sample of Canadian sex offenders (n = 710), the Risk Matrix 2000/Sex, /Violence and /Combined scales significantly predicted the six recidivism outcomes: sexual, any sexual (including sexually motivated breaches), non-sexual violent, violent, any crime (excluding breaches) and any recidivism (including breaches). Area under the receiver operating characteristic curve (AUC) values were moderate to large. The STABLE-2007 generally added incremental predictive validity to the Risk Matrix 2000. Structured rules and recidivism estimates are provided for combining the two scales. The current study illustrates that predictive accuracy can be improved by combining static and dynamic risk scales in a structured manner.