The Philadelphia Pretrial Service Division is testing Global Positioning Surveillance as a monitoring device to keep track of high-risk defendants and probationers under community supervision.

The GPS tracking system consists of a tamper-resistant ankle bracelet transmitter worn by the offender and a belt-mounted GPS tracking unit worn when the person is away from home. The tracking unit is about the size of a cell phone.

In addition to tracking a person’s whereabouts, the system monitors whether he or she has entered any off-limits areas during specific time periods, defined by a map created for each individual. For example, playgrounds during school hours would be off limits for sex offenders. If a supervised person enters an area when not permitted, officials are notified to investigate.

Patricia Farrell, electronic monitoring coordinator for the Philadelphia Pretrial Service Division, says the method has not been adopted for longterm use, but could prove a useful monitoring device. “GPS tracking will not prevent crime,” she says, “but it will provide a very high degree of detail about a person’s activities so we can intervene if necessary.”

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