April 20, 2010

New study: Do popular actuarials work?

Newer instruments outperform Static-99 and RRASOR

If you evaluate sex offenders, you may be overwhelmed by the dizzying array of actuarial risk assessment instruments vying for your vote: Static-99, RM 2000, RRASOR, Static-2002, SORAG, MnSOST-R. The list of weird-looking acronyms grows ever longer, and the validity studies more complex.

For help figuring out which instruments do what, and how well, I recommend a study by two Canadians, Jan Looman and Jeffrey Abracen, just published in the Journal of Interpersonal Violence. The study compared the ability of four leading instruments to predict recidivism among a sample of 419 high-risk Canadian sex offenders. Overall, about 15% of the released offenders were convicted of a new sex offense when the follow-up time period was held at a constant of seven years.

Among the interesting findings:
  • When rapists and child molesters were examined separately, none of the instruments were able to predict sexual recidivism (defined as a new conviction) for child molesters.
  • The RRASOR (Rapid Risk Assessment for Sex Offense Recidivism) bombed completely as a predictive tool. The Static-99, a descendant of the RRASOR and the most widely used actuarial for assessing sex offender risk, did not do much better. As the authors note, since their sample was similar to U.S. offenders subject to civil commitment as Sexually Violent Predators (SVPs), the lack of predictive validity of these instruments raises concerns about their use in SVP proceedings.
  • Two newer instruments -- the Static-2002 and the Risk Matrix 2000, developed in England -- did somewhat better. Especially interesting is how the Static-2002 performed. Overall, only two of the instrument's five subscales predicted sexual recidivism. Not surprisingly, these were Age at Release and Persistence of Sexual Offending. This is rather common sensical, in that sex offending declines dramatically with age, and a high score on the Persistence scale indicates an entrenched pattern of sex offending, with an early onset, a high rate, and multiple convictions. When rapists and child molesters were separated out, instead of being lumped together as generic “sex offenders” as they often are, only the Deviant Sexual Interests scale predicted sexual recidivism for the child molesters.
  • Finally, age matters. It really does. The few who continue to deny this obvious fact are just being stubborn. Similar to other studies, only about 2% of offenders over 50 reoffended (one child molester and one rapist, in this case), compared with 20% of those ages 25 to 35.
Of course, this is just one study. Other studies comparing the accuracy of instruments for assessing sex offender risk have come to various and contradictory conclusions. For example, contrast the present findings with those of the Austrian study that I blogged about last month, testing German versions of the RRASOR, Static-99, SORAG, and SVR-20. The publisher of the International Journal of Offender Therapy and Comparative Criminology has just made that study available for free, by the way. Keeping up with this burgeoning literature is a full-time job, unfortunately necessary for practice in this area.

The abstract of the study, Comparison of Measures of Risk for Recidivism in Sexual Offenders, is available at the Journal of Interpersonal Violence's website. You need a subscription to get the entire article, or you can request a copy from the authors.

Prospective Actuarial Risk Assessment: A Comparison of Five Risk Assessment Instruments in Different Sexual Offender Subtypes, by Martin Rettenberger, Anna Matthes, Douglas P. Boer, and Reinhard Eher, is available for free from the International Journal of Offender Therapy and Comparative Criminology. Thanks for that go to journal editor Thomas Mankowski.

1 comment:

Anonymous said...

Nice summary Karen. Now if added scientific armamentarium could loosen the stranglehold of a pretextual system that endorses reinforced erroneous "common sense" views about SVPs.

Roy Aranda, Psy.D, J.D.
New York