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Revisiting Risk Assessment with Sexual Offenders: Validation and Extension of the STATIC-99 and Penile Plethysmograph with a Community Sample

23 July 2010


The ability of the Static-99 and dimensional measurement of penile plethysmograph (PPG) to predict conviction for new general or sexual offenses was assessed with a community sample. Because deviant sexual arousal is theoretically a dynamic risk factor and treatment target, this study proposed that adding the PPGmeasured deviant arousal to the Static-99 would improve the predictive quality of the actuarial measure. Records for 131 subjects who presented for psychosexual evaluations at a community sex offender treatment facility were examined to collect relevant data and score the Static-99, and conviction information was obtained from the Oregon Department of Corrections. These data were examined using logistic regression to determine the predictive validity of the Static-99, predictive qualities of the PPG, and incremental validity of adding PPG information to the Static-99. Contrary to previous studies examining the Static-99 and PPG separately, results indicated that there were no statistically significant relationship between Static-99 scores, PPG percent deviant arousal, and any new sexual or general convictions. Similarly, the addition of the PPG results to the Static-99 offered no statistically significant increase in predictive abilities. The Static-99 and PPG results performed at chance when predicting recidivism, either generally or sexually, when examined in a community setting. In order to produce more reliable measures of recidivism with offenders released in the community, the Static-99 norms and items, as well as the interpretation and utility of PPG results, must be revisited and refined.


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