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GPS Monitoring Practices

GPS Monitoring Practices

GPS Monitoring Practices in Community Supervision and the Potential Impact of Advanced Analytics
By The National Criminal Justice Technology Research, Test, and Evaluation Center
Published: 07/04/2016
GPS Monitoring Practices in Community Supervision The following has been reprinted from a January 2016 report by The National Criminal Justice Technology Research, Test, and Evaluation Center and prepared for The National Institute of Justice.


The first electronic monitoring (EM) devices were developed in the 1960s with the intent of providing feedback to young-adult-offender volunteers to facilitate their rehabilitation, but that approach was not widely accepted (Reference [1])[1]. Following their reemergence in the 1980s in support of a more punitive model of offender treatment, such devices were used principally for home detention applications. By 1990 radio-frequency (RF)[2] technologies were in-use in all 50 states (Reference [2]).

The utility of EM increased considerably in 2000 when the military began permitting civilian Global Positioning System (GPS) receivers to attain much greater accuracy (Reference [3]), and the offender tracking market expanded quickly.[3] At least 44,000 tracking devices were estimated to be in-use in the United States by 2009 (Reference [5]), and the more compact and affordable devices available today can be better tailored to specific needs. Modern features include voice communication, and audible and vibratory alerts to warn participants of schedule violations. These devices also include improved case management software and better mapping technology, with playback capabilities and mobile restriction zones that can be used to keep tracked participants from congregating and separated from former victims (Reference [6]).

Much of the exigency for enhanced usage of offender monitoring systems has resulted from legislative mandates to track sex offenders, but other applications have emerged such as intensively supervising high-risk parolees, developing confinement alternatives for low-risk criminals to facilitate their re-entry into society and alleviate jail overcrowding, or monitoring pre-trial defendants. “By 2010, 33 states had enacted legislation requiring that this technology be used on sex offenders,” although many had not yet implemented those programs (Reference [6]). Some states and jurisdictions had also begun using EM to track gang members and domestic abusers, monitor habitual burglars, or alert former victims when offenders were released from custody (References [3] and [7]). Nevertheless, GPS-based systems generate a plethora of data. Without analytical aids to interpret those data, supervising agents can quickly become overwhelmed and unable to take advantage of these tools as they manage their daily caseloads.

The temporal sequences of locations gathered by GPS monitoring systems provide unprecedented opportunities to explore patterns of activity through the application of space-time analytics to individual movements and stops (Reference [8]). Automated processing and alerting algorithms developed to more fully exploit gathered data could focus an agent’s attention on only those events requiring investigation, and provide the basis for conducting social network analyses to gain intelligence on offender habits (Reference [9]). While analytical capabilities do not appear to have strongly influenced correctional agency selection of their EM vendors and products to date, tools comprising various combinations of statistical analysis procedures, data and text mining, and predictive modeling can be mission enabling through the discovery of hidden behavioral patterns and the prediction of future outcomes.

This paper briefly reviews research on the usage of location-based tracking to motivate an assessment of the potential role of advanced analytics in more strongly leveraging the capabilities of such systems. Relying in part on the results from a recent market survey of commercially-available analytics products suitable for use in correctional applications (Reference [10]), it presents several recommendations for deriving actionable information from GPS tracking data as an aid to managing community-released offender populations. Nevertheless, “… there has been little rigorous research evaluating the impacts of electronic monitoring,” and questions remain about the efficacy of this approach in community supervision. “Policy-relevant research” is needed that is “focused toward understanding the potential for supervision with electronic monitoring to improve long-term outcomes” (Reference [11]).


In spite of the fact that there has been “… little scientific research documenting the effectiveness of electronic monitoring devices, especially for sex offenders” (Reference [12])[4], the number of early-release candidates has increased over the last 15 years. Early-release programs can reduce incarceration costs and jail overcrowding, and GPS devices render clients highly accountable, although “[e]lectronic supervision technologies by themselves do not foster pro-social behavior (or) reduce recidivism….” However, “[w]hen implemented and operated within an overall strategy of behavioral modification … there is the potential for some electronic supervision tools to enhance community supervision” outcomes (Reference [4]). A recent Danish study by Andersen and Andersen on the social welfare dependence of serving a sentence under electronic monitoring rather than in prisons supports this view. Those authors found that “[e]lectronic monitoring is less harmful than imprisonment on the life-course outcomes of offenders.” They conclude that because EM could be less costly than incarceration, “efforts to extend the use of electronic monitoring in the United States could be accelerated” (Reference [14]).

A review of state codes during the late 2000’s by Button et al. (Reference [12]) found that 46 states and the District of Columbia had “some type of legislation governing the use of electronic monitoring;” an extensive summary of the legislative patterns found by these authors appears in their Table 1[5]. Of these 47 “states,” 27 had “specific policies for monitoring sex offenders, with 19 of these states requiring electronic monitoring for sex offenders.” In an early 2015 news article, Wolf (Reference [15]) claimed that “[m]ore than 40 states have passed laws in the last decade that call for some type of GPS monitoring of sex offenders, including eight states that monitor them for life…. At least 13 states monitor domestic abusers.” However, Payne (Reference [16]) indicated privately that he was unaware of any recent efforts to update the numbers shown in references [2], [4], and [12].

Drake (Reference [5]) lists six application areas in which offender tracking technology offers an attractive option, and an additional category has been added below based on modern usage:

  • Sex Offenders: By 2009, California parole officials were electronically monitoring approximately 7,000 sex offenders, as well as several thousand more probationers. Sex-offenders in California communities were still being GPS-monitored at those levels in mid-2011. This corresponds to more than three times the number of units used by Florida, which was the state using the second-largest number of such devices at that time (Reference [3]).
  • Gang Disruption: California also implemented an aggressive program for monitoring high-risk gang members during the first decade of this century (References [3] and [17]). Tracking technology can identify gang-member violations of established exclusion zones, and their movements can be used to define mobile exclusion zones for other gang members, and indicate previously-unknown social network connections.
  • Domestic Violence: Offender-tracking technology is effective for enforcing temporary restraining orders. By 2009, Michigan and Massachusetts had developed very aggressive programs using tracking technology to keep offenders away from their former victims, and at least two vendors had developed systems that could be used to track both offenders and victims, permitting the victim’s location to be used as a mobile exclusion zone for the offender.
  • Jail Overcrowding: To help avoid law suits by advocacy groups for the incarcerated that demand less-crowded living conditions, many jurisdictions have begun community supervision programs for low-risk offenders, which often utilize offender tracking.
  • Habitual Offenders: Some jurisdictions use remote surveillance equipment to track chronic and troublesome offenders. A related application that was used as early as 2009 by Midland and Dallas, Texas involves the selective tracking of habitually truant students.
  • Crime-scene Correlation: GPS tracking technology has great potential for facilitating automated crime-scene analyses by allowing crime-scene data collected by cooperating law enforcement agencies to be cross-referenced with the location history of all offenders being monitored. While only two vendors offered that broad capability in 2009, most system vendors provided at least simple correlation software as part of their basic service that allowed the address of a single crime scene to be checked against the recorded locations of all offenders being monitored.
  • Pre-trial supervision: GPS monitoring systems are used at both state and federal levels for pre-trial supervision of individuals awaiting court appearances. For example, U.S. Immigration and Customs Enforcement monitor thousands of people awaiting adjudication by the judicial system.

[1] The authors of Reference [1] speculated that EM technology did not gain traction at that time because social acceptance was lacking for using positive reinforcement to change behavior, and because of an “Orwellian” fear of using electronic technology to remotely monitor individuals. They also noted that in the pre-digital era of the mid 1960’s when this work occurred, EM represented such a substantial departure from then-existing correctional practices that it was difficult for most practitioners to conceptualize its use.
[2] Definitions for all of the abbreviations and acronyms used in this document are presented in Appendix A.
[3] Although the term “electronic monitoring” was traditionally associated with “curfew monitoring” of individuals confined to their homes (or other locations) by RF-based systems, it is also used today as a synonym for location-based tracking with GPS technology. Some authors (e.g., Reference [4]) embed these terms within the broader category of electronic supervision, which encompasses a larger array of technologies that includes crime-scene correlation and remote alcohol monitoring.
[4] The most thorough review of such work (at least as of the 2009 publication date of this reference) was conducted by Renzema and Mayo-Wilson (Reference [13]).
[5] Colorado, Kentucky, Minnesota, and Nevada did not have some type of legislation governing the use of EM as of that date. To view the full report click here.



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