Study
Grommon and colleagues (2017) used a retrospective quasi-experimental design to examine the impact of pretrial global positioning system (GPS) supervision on defendants arrested on intimate partner violence (IPV) charges. The study was conducted in a pretrial services division of a city and county community corrections department in a large jurisdiction, of approximately three million residents, in the western region of the United States. The intervention was evaluated to examine failure to appear in court, pretrial services meetings, and rearrests outcomes, compared with defendants assigned to pretrial supervision without GPS technology.
The study consisted of a total of 1,483 defendants assigned to either GPS supervision or basic pretrial supervision. Of the defendants who participated in the study, 85 percent were male, 71 percent were white, and 37 percent were Hispanic, and the average age was 34 years. The treatment group (n=573) received an ankle unit that monitored a defendant’s movements while awaiting trial. An assigned pretrial officer was notified when a defendant violated any of the exclusion zones. The control group (n=910) received traditional pretrial supervision but was still required to have contact with pretrial services through telephone check-ins and case management meetings.
Two different information systems were used to maintain defendant records. One system-maintained records about defendants referred to the court and documented the period between jail booking and the bonding decisions made at the initial hearing. The second system detailed court and supervision activity. Both systems were used to access demographic, criminal history, instant offense, risk assessment, bond recommendation, and bond order information.
Four different outcomes were measured to determine pretrial misconduct. Failure to appear in court was defined as a defendant’s failure to appear at a scheduled court hearing. Failure to appear at a meeting was defined as a defendant’s failure to attend a scheduled meeting with the assigned pretrial officer. Rearrests were defined as any new arrest for any new offense. Domestic rearrests were defined as any new arrest for a domestic violence offense, including violations of protection or court orders.
A Cox regression model was used to compare pretrial misconduct between those defendants on GPS supervision and those receiving basic pretrial supervision. A chi-square and ANOVA models were used to assess baseline differences between the treatment and control groups. There were statistically significant differences between treatment and control groups at baseline. Defendants in the treatment group had more serious charges, higher risk scores, more contact with the criminal justice system, and received higher bond amounts. The study addressed the limitations by using different methods to reduce bias in the sample, including propensity score matching strategy using the Mahalanobis distance and the marginal mean weighting through stratification (MMW-S). It is the MMW-S procedure that produced the most equivalent comparison group, to assess the effect of GPS supervision. The outcomes presented below relate to the MMW-S method. No subgroups were analyzed.
