Monitoring High-Risk Sex Offenders with GPS Technology: An Evaluation of the California Supervision Program

April 2012 California:

Abstract:
Despite the increasing number of high-risk sex offenders (HRSOs) who are being placed on electronic monitoring programs, little is known about how effective these programs are in increasing offender compliance and in reducing recidivism. The purpose of this evaluation is to determine the effectiveness of the global positioning system (GPS) monitoring of HRSOs who are released onto parole.

This study integrates outcome, cost, and process evaluation components. The outcome component assesses the impact of the California Department of Corrections and Rehabilitation’s GPS supervision program by employing a nonequivalent-group quasi-experimental design with a multilevel survival model. We also use a propensity score matching procedure to account for the differences between the treatment and comparison groups. The study population is drawn from all HRSOs who were released from prison between January 2006 and March 2009 and residing in the state of California. The final sample includes 516 subjects equally divided between the treatment and control groups. The treatment group consists of HRSOs who were placed on GPS monitoring. The control group is made up of similar offenders who were not placed on the GPS system during the study period. The resulting sample shows no significant differences between the groups on any of the propensity score matching variables.

The effectiveness of the program is assessed using an intent-to-treat (known as ITT) approach. The two main outcomes of interest are compliance and recidivism. Compliance is measured through violations of parole. Recidivism is assessed in a variety of ways, including 1) rearrest, 2) reconviction, and 3) return to prison custody. Each outcome is assessed with a survival analysis of time-to-event recidivism data, using a Cox proportional hazards model. In addition, we use frailty modeling to account for the clustering of parole agents within parole districts.

The findings indicate, despite the baseline similarities, a clear pattern of divergence in outcomes during the 1-year study period. The subjects in the GPS group demonstrate significantly better outcomes for both compliance and recidivism. In terms of compliance, the multivariate model shows that the hazard ratio of a sex-related violation is nearly three times as great for the subjects who received traditional parole supervision as for the subjects who received the GPS supervision. In terms of recidivism, compared with the subjects who received the GPS monitoring supervision, the hazard ratio for any arrest is more than twice as high among the subjects who received traditional parole supervision. Similarly, for both a parole revocation and any return-to-custody event, the hazard ratio suggests that these events are about 38 percent higher among the subjects who received traditional parole supervision.

The cost analysis indicates that the GPS program costs roughly $35.96 per day per parolee, while the cost of traditional supervision is $27.45 per day per parolee—a difference of $8.51. However, the results favor the GPS group in terms of both noncompliance and recidivism. In other words, the GPS monitoring program is more expensive but more effective.

Finally, the process evaluation reveals that the GPS program was implemented with a high degree of fidelity across the four dimensions examined: adherence, exposure, quality of program delivery, and program differentiation. ..Source.. by California DOC