GPS criminal offender supervision has been around for awhile, but it made national news a few months ago when Martha Stewart donned an electronic monitoring bracelet to track her movements during a five-month house arrest at her 153-acre estate. The monitoring system allows police to track Stewart's movements both at her $16 million estate and during the 48 hours a week she is allowed to leave her home to shop or carry out other approved errands.

While not every offender will have the prominence of Martha Stewart, recent innovations in technology combined with the U.S. Military's Global Positioning System (GPS) have pushed GPS criminal offender supervision to the forefront for community corrections agencies, typically charged with monitoring probationers, parolees and pretrial defendants. Such advancements have many community corrections agencies taking a second look at GPS tracking.

GPS offender tracking, as with more traditional house arrest electronic monitoring systems, is being used for community supervision and as a viable sanction for judges seeking an alternative to incarceration. It is also for community corrections agencies wanting an extra layer of detail about a person's activities when they are being supervised in the community. In general, offender monitoring has grown in importance over the last few years due to increasingly tighter budgets, overcrowded prisons and jails, and a shift toward moving nonviolent offenders back to the community, where they can be closely supervised using modern technology, versus the much more costly alternative — incarceration.

GPS tracking takes offender supervision to the next level. When police officers encounter a suspect wearing one of these devices, it makes sense for them to understand what these systems are, how they operate, what they can and cannot do, and finally, what procedures agencies using these systems would suggest you follow.

GPS offender tracking systems have many common components. To date, all GPS tracking systems have a GPS tracking unit worn by the offender on a belt when they leave home, an ankle bracelet transmitter, a charging base station in the individual's home and a central monitoring computer system.

• GPS tracking unit. These units vary in size and weight, with some original tracking units weighing almost 5 pounds. These units have been shrinking, though, with the newest GPS tracking unit on the market, BI ExacuTrack, weighing in at 9 ounces. All systems gather GPS data points while the offender moves about the community. The GPS tracking unit must be "visible" to three GPS satellites at one time to provide an accurate position for the offender. Typically, eight to 12 of the 24 satellites in the U.S. Military's constellation of GPS satellites are visible at any one time to the GPS tracking unit, providing many redundant observation vantages. When the person leaves home, the GPS tracking unit must not become separated from the ankle bracelet transmitter or an alert is issued.
• Ankle bracelet transmitter. The ankle-mounted bracelet transmitter is an extension of traditional, proven technology — radio-frequency electronic monitoring systems that monitor the absence or presence of a person, usually at home. When the GPS tracking unit is added to the mix, the ankle bracelet creates an electronic bond to this device. The ankle transmitter is tamper-resistant. That doesn't mean an offender cannot remove it; it simply means if it is tampered with, monitoring specialists will know and can then notify the community corrections agency.
• Charging base station. The charging base station, sometimes called a docking station, is plugged into an AC power outlet and a standard phone jack in the offender's residence. It appears similar to a home telephone system. The system can both download and relay GPS data points to the central monitoring computer.
• Central computer and monitoring corrections. The central monitoring computer maintains offender details and schedules for each person on GPS tracking. Agencies will define geographic zones the offender may or may not enter (called "inclusion" and "exclusion" zones). The monitoring computer will issue violation alerts, if necessary, when a person breaches the conditions of release. The corrections also must be able to translate an offender's GPS data points logged as he or she moves through the community and overlay those onto an easy-to-read mapping system.

Sometimes, violations to the parameters laid out for the offender can be noted and forwarded to the agency within minutes — this type of system has been labeled an "active" GPS system — while other systems log GPS data points while the person travels through the community then downloads that information to be analyzed when the person returns home and places the GPS tracking unit in the charging base station. Each system has pros and cons, but usually the systems that download the data once or twice a day provide sufficient detail for uncovering the patterns of activity that the supervising officer must address with the offender.

On the surface, it may seem most helpful for agencies to know within minutes if an offender has violated their conditions of release by leaving an inclusion zone or entering an exclusion zone. However, some agencies are leery of active GPS systems. So much information, they say, can lead to "data overload" that can have the agency responding daily to continuous violation notifications, some of which are simply nuisance violations. To the police officer on the street, there will be little if any noticeable difference to these systems, other than size.

A major drawback voiced about active GPS systems is the misperception that a community corrections or police officer can intervene to thwart criminal activity. That is simply not the case, as few agencies have dedicated resources waiting for such a call nor could they move from office to "potential" crime location before a crime is committed.

What both active and passive GPS systems can provide, though, is important and concrete details about offender behavior while they move within the community. As a result, patterns in behavior can be detected and addressed, with the hope that future crime can be prevented. GPS systems can provide correlation to crime scenes and can alert local police officers if offenders are associating with other GPS-tracked individuals while in the community.

Most community corrections agencies have outlined procedures and protocols for what local police should do when encountering an offender on GPS tracking, according to Jim Buck, a senior product manager for BI Inc., a Boulder, Colorado, provider of electronic supervision equipment and services. Buck, who heads up BI's GPS product development team, has helped agencies educate local police officers on what these systems are — and are not — and best practices for managing offenders being monitored with GPS.

For example, if a police officer encounters a person on GPS, it will be fairly apparent the person is on some type of monitoring system. The officer will probably notice an ankle bracelet or belt-mounted GPS tracking unit, or the individual may simply offer this information. If the officer decides to detain the person, it is important to identify what agency is supervising the individual and the person's supervising probation or parole officer. Individuals on GPS tracking will know their supervising officer's contact information, according to Buck.

If the person is to be booked, as with traditional electronic monitoring equipment, the GPS equipment will typically be removed before the individual is processed for secure detention. Contacting that supervising officer is a best first step, even before processing the suspect. The equipment does not need to be removed if the person is not going to be detained, Buck suggests.

In the event a suspect is processed for arrest, officers should understand that none of the equipment poses a danger or threat to the individual or to the officer. "Officers should not have any concerns about cutting the ankle bracelet, provided it can be safely stored along with the GPS tracking unit until returned to the overseeing authority," Buck says. If the offender is uncooperative in identifying their supervising agency, contact the equipment's manufacturer, which can identify the agency.

If police opt to remove a person's ankle bracelet or GPS tracking unit, it is easier to remove the equipment in a secure facility, where the officer can control the environment. Removing the system in the field or transporting a suspect through a location they are not supposed to go, such as near a school, may trigger an audible alert or alarm. "Officers should not be alarmed in either case," says Buck. "Simply contact the supervising agency and they can deactivate the system."

Upon returning the equipment to the overseeing agency, a verifiable account of the individual's GPS trail can be downloaded by docking the GPS tracking unit to the charging base station in the offender's home. This can actually provide valuable information to police, such as whether a suspect was within the vicinity of a crime scene, since the GPS data points can be precisely matched to street locations within meters. This data is court admissible, if needed.

As with any system, though, each corrections or law enforcement agency will follow protocols that work for their situation. In Roanoke County, Virginia, the sheriff's department has used electronic monitoring to help reduce jail overcrowding. Today, the Roanoke Home Detention Program, using both GPS and traditional electronic monitoring, includes almost 10 percent of its jail's population. These individuals are community-based prisoners who have been released to community supervision to relieve overcrowding, produce savings for the community, and allow these individuals to work and support their families versus taking up valuable jail space.

Sgt. Brian Keenum, who oversees the Roanoke Home Detention Program, says GPS tracking is used for individuals released to the community who need an extra level of accountability. He encourages law enforcement officials who encounter an individual on GPS tracking to contact his department immediately if a person is to be detained. Once contacted by an arresting officer, jail or booking agent, Keenum will meet the suspect and arresting officer at the designated location and remove the equipment with a specific unlocking tool, thereby preventing a trip to the manufacturer for replacement or repair. He will also go to the individual's home, insert the GPS tracking unit in the charging base station and download that offender's GPS data points.

Roanoke officials like the GPS tracking system, and use the GPS maps to discuss a person's behavior and patterns of activity with local judges and the offender's themselves. Importantly, Keenum's department has begun — and hopes to expand — educational training seminars about GPS systems locally. These outreach efforts will include communicating with local police. "We need to do more training for local departments on the program's abilities, what offenders are on these systems and who to contact for more information," he explains.

In Boulder County, Colorado, the local sheriff's office also operates a home detention program that includes the use of electronic supervision technology. The department recently tested GPS offender tracking. Deputy Sheriff Bill Weiss says most police officers in the region who come in contact with a person on electronic monitoring or GPS will know to contact the sheriff's department. The officer can find out who is supervising the individual through a statewide database of all offenders, current and past. "We encourage police officers to contact us first, before trying to remove the equipment," Weiss says. "Officers really don't need to do anything differently for a person on one of these systems, simply contact us and we will meet them and determine if equipment should be removed."

GPS systems for offender supervision are an important tool for community corrections agencies. These systems will help deliver information not previously available, namely a verifiable, accurate record of an offender's movement during each day. It is important for local police to be able to recognize these systems, be familiar with their capabilities and know who to contact if they need more information about them. This understanding should reap rewards for the community corrections agency, local police and public safety efforts.

Patrick Hyde and Nicole DeJarnatt are freelance writers based in Boulder, Colorado.