Judge bars Static-99R risk tool from SVP trial
Developers staunchly refused requests to turn over data
For several years now, the developers of the most widely used sex offender risk assessment tool in the world have refused to share their data with independent researchers and statisticians seeking to cross-check the instrument's methodology.
Now, a Wisconsin judge has ordered the influential Static-99R instrument excluded from a sexually violent predator (SVP) trial, on the grounds that failure to release the data violates a respondent's legal right to due process.
The ruling may be the first time that the Static-99R has been excluded altogether from court. At least one prior court, in New Hampshire, barred an experimental method that is currently popular among government evaluators, in which Static-99R risk estimates are artificially inflated by comparing sex offenders to a specially selected "high-risk" sub-group, a procedure that has not been empirically validated in any published research.
In the Wisconsin case, the state is seeking to civilly commit Homer Perren Jr. as a sexually dangerous predator. Perren just completed a 10-year prison term for an attempted sexual assault on a child age 16 or under.
The ruling by La Crosse County Judge Elliott Levine came after David Thornton, one of the developers of the Static-99R and a government witness in the case, failed to turn over data requested as part of a Daubert challenge by the defense. Under the U.S. Supreme Court's 1993 ruling in Daubert v. Merrell Dow Pharmaceuticals, judges are charged with the gatekeeper function of filtering evidence for scientific reliability and validity prior to its admission in court.
Defense attorney Anthony Rios began seeking the data a year ago so that his own expert, psychologist Richard Wollert, could directly compare the predictive accuracy of the Static-99R with that of a competing instrument, the Multisample Age-Stratified Table of Sexual Recidivism Rates," or MATS-1. Wollert developed the MATS-1 in an effort to improve the accuracy of risk estimation by more precisely considering the effects of advancing age. It incorporates recidivism data on 3,425 offenders published by Static-99R developer Karl Hanson in 2006, and uses the statistical method of Bayes's Theorem to calculate likelihood ratios for recidivism at different levels of risk.
The state's attorney objected to the disclosure request, calling the data "a trade secret."
Now, a Wisconsin judge has ordered the influential Static-99R instrument excluded from a sexually violent predator (SVP) trial, on the grounds that failure to release the data violates a respondent's legal right to due process.
The ruling may be the first time that the Static-99R has been excluded altogether from court. At least one prior court, in New Hampshire, barred an experimental method that is currently popular among government evaluators, in which Static-99R risk estimates are artificially inflated by comparing sex offenders to a specially selected "high-risk" sub-group, a procedure that has not been empirically validated in any published research.
In the Wisconsin case, the state is seeking to civilly commit Homer Perren Jr. as a sexually dangerous predator. Perren just completed a 10-year prison term for an attempted sexual assault on a child age 16 or under.
The ruling by La Crosse County Judge Elliott Levine came after David Thornton, one of the developers of the Static-99R and a government witness in the case, failed to turn over data requested as part of a Daubert challenge by the defense. Under the U.S. Supreme Court's 1993 ruling in Daubert v. Merrell Dow Pharmaceuticals, judges are charged with the gatekeeper function of filtering evidence for scientific reliability and validity prior to its admission in court.
Defense attorney Anthony Rios began seeking the data a year ago so that his own expert, psychologist Richard Wollert, could directly compare the predictive accuracy of the Static-99R with that of a competing instrument, the Multisample Age-Stratified Table of Sexual Recidivism Rates," or MATS-1. Wollert developed the MATS-1 in an effort to improve the accuracy of risk estimation by more precisely considering the effects of advancing age. It incorporates recidivism data on 3,425 offenders published by Static-99R developer Karl Hanson in 2006, and uses the statistical method of Bayes's Theorem to calculate likelihood ratios for recidivism at different levels of risk.
The state's attorney objected to the disclosure request, calling the data "a trade secret."
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