Actuarial Assessment of Sex Offender Recidivism Risk: A Cross-Validation of the RRASOR and the Static-99 in Sweden

We cross-validated two actuarial risk assessment tools, the RRASOR (R. K. Hanson, 1997) and the Static-99 (R. K. Hanson & D. Thornton, 1999), in a retrospective follow-up (mean follow-up time = 3.69 years) of all sex offenders released from Swedish prisons during 1993–1997 (N = 1,400, all men, age 18 years). File-based data were collected by a researcher blind to the outcome (registered criminal recidivism), and individual risk factors as well as complete instrument characteristics were explored. Both the RRASOR and the Static-99 showed similar and moderate predictive accuracy for sexual reconvictions whereas the Static-99 exhibited a significantly higher accuracy for the prediction of any violent recidivism as compared to the RRASOR. Although particularly the Static-99 proved moderately robust as an actuarial measure of recidivism risk among sexual offenders in Sweden, both procedures may need further evaluation, for example, with sex offender subpopulations differing ethnically or with respect to offense characteristics. The usefulness of actuarial methods for the assessment of sex offender recidivism risk is discussed in the context of current practice.