Electronic Monitoring Devices in Criminal Justice: A Complete Guide

Introduction to Electronic Monitoring Devices

Electronic Monitoring Devices (EMDs) are devices used for the electronic monitoring of criminals and other groups suspected of involvement in illegal activity, including defendants under trial on conditional release and offenders already convicted who are on probation or parole. Technically, electronic monitoring (EM) is a generic term covering a broad spectrum of systems and components. Many vendors dominate the industry, each offering a range of choices covering home monitoring devices, field monitoring devices, wrist and ankle bracelets, voice verification systems, and alcohol testing devices. EM systems are classified as either active or passive. Active systems are by far the most popular and dependable; the transmitter sends a continuous signal to the Home Monitoring Device (HMD). (National Law Enforcement and Corrections Technology Center, 1999)

The HMD alerts the central monitoring center if the offender travels beyond the designated range. In a passive system, the offender is typically required to speak with a case official by telephone or place the transmitter into the HMD to confirm attendance. Active systems track the location of an offender on a continuous basis. Among the newest systems are those using Global Positioning System (GPS) technology to observe the offender around the clock in any location. Each type has its own relative advantages and disadvantages.

Voice Verification Systems, regarded as passive, require an offender to respond to a home-based phone call, creating electronic voice prints that determine whether the offender's voice during a routine verification call matches the voice recorded at program enrollment. An additional passive system requires the offender to exhale into a device at home for detecting the presence of alcohol in the blood. (National Law Enforcement and Corrections Technology Center, 1999)

EMDs are composed of several integrated system components that work together to assess and monitor offenders.

When an offender is placed under house arrest, a HMD is installed in the home for use with a transmitter that the offender keeps attached to his or her person at all times. The HMD operates through the telephone line and jack. It is also equipped with tamper-detection capabilities, power-outage detection, memory retention so that it can report all saved messages upon restoration of electrical power, and an internal antenna in the event the offender attempts to tamper with it. The HMD requires a 120-volt outlet for adequate power and must not be excessively large or heavy. (National Law Enforcement and Corrections Technology Center, 1999)

Types of Electronic Monitoring System Components

Transmitters are worn by offenders on the wrist or ankle to signal the offender's whereabouts. To be effective, they must be light and easy to wear. They must be shockproof and waterproof, allowing the offender to work and bathe without damaging the internal components or overall structure. They must also be tamperproof so that the offender cannot interfere with their functioning. One particular type resembles a buckle of a seatbelt connected to a sports watch, with a cable running through the band that snaps if the device is removed. Because the transmitter is shockproof and waterproof, it does not need to be removed during daily routines. If it is removed, police are alerted through an alarm.

For a home unit, it is not always necessary for all transmitters to be connected. A transmitter from one manufacturer looks almost like a watch and transmits a signal approximately seven times a day, prompting the offender to call the telephone number displayed on the watch. Upon receipt of the message, the host computer identifies the person, their phone number, and whether the offender has tampered with the watch. A daily report provides a detailed account of all calls and instances of tampering. (National Law Enforcement and Corrections Technology Center, 1999)

A Field Monitoring Device (FMD) is a verification unit that provides the ability to confirm that an offender is wearing a transmitter while in public. FMDs are highly flexible: they are relatively small, lightweight, and operate within a range of at least 100 feet. They can be handheld or mounted on the roof of a vehicle. Through an FMD, a case officer can identify an offender's name and location simply from the transmitting number, as well as determine whether the bracelet has been tampered with. This type of on-site verification is important to a successful Electronic Monitoring Program (EMP), as it helps guarantee both public safety and offender compliance. FMDs also allow officials to respond quickly to EM violations and check on offenders without their knowledge. Some FMDs sold commercially are capable of tracking up to 1,000 events, which can be downloaded to a host computer for a complete event record. (National Law Enforcement and Corrections Technology Center, 1999)

Offenders placed under monitoring are typically prohibited from consuming alcohol; therefore, many EMPs require alcohol testing to ensure that program participants refrain from drinking. If an offender tests positive for alcohol, the HMD transmits a message alerting the monitoring center to the violation, and the monitoring center then sends an alert to the EMP. If a reading is positive, the HMD normally requests a repeat reading to guard against false positive reports. If the second reading is also positive, EMP staff must visit the offender's home to conduct a field test. (National Law Enforcement and Corrections Technology Center, 1999)

Voice verification is an important component of many EMPs. Although it may require a lengthy setup period, the initial investment in time pays off over time. Once operational, the unit can test the offender's voice pattern repeatedly throughout the day with a high degree of accuracy. During enrollment in a voice verification program, the offender's voice is recorded as an electronic voice print and saved at the monitoring center for later review by EMP staff. Programs require offenders to speak a short sentence or phrase, as a single word would not accurately record their presence. At each call, the caller's voice is matched against the voice print on file. The system can also analyze background sounds to detect whether the offender is in the location where he or she is required to be. (National Law Enforcement and Corrections Technology Center, 1999)

For verification purposes, offenders may be required to call the monitoring center, or they may receive a call asking them to state their date of birth, the time, or their social security number. They may also be asked to repeat the sentence or phrase recorded at enrollment. If the offender provides false personal information or the phrase does not match the recorded one, the offender fails the test and the monitoring center is alerted. Most EMPs apply voice verification together with, and immediately prior to, the alcohol test—primarily to ensure that the person taking the test is indeed the offender. Several EMPs allow officials to call an 800 number to listen to a recording of the offender's voice verification test. (National Law Enforcement and Corrections Technology Center, 1999)

House arrest, or home confinement with electronic monitoring, is an intermediate community corrections program designed to restrict the activities of offenders within the community. This provision allows offenders to remain in their own homes and continue their routine duties. Their activities are regularly monitored either through electronic means or through periodic staff contacts to ensure that their actions comply closely with those stipulated by the court. Offenders placed under home confinement remain confined to their homes for varying time periods and must maintain a strict daily schedule. There are generally two types of home confinement programs: pre-trial and post-adjudication. Pre-trial programs use home confinement as a substitute for jail to ensure that individuals appear in court. Post-adjudication programs use home confinement as a sanction that is harsher than routine supervision yet less restrictive than incarceration. (Model Programs Guide, n.d.)

House arrest began as a program designed specifically as a sentencing alternative for drunk drivers, but rapidly spread to other offender populations across many jurisdictions. Depending on the nature of the crime, home confinement has been designed with varying degrees of restriction, ranging from ordinary curfews to complete confinement. For instance, the home confinement program of the federal courts provides three separate levels of restriction under U.S. Probation and Pretrial Services (2000). Under the first level—curfew—participants are required to remain at home during certain hours each day. Under the second level—house arrest—participants must remain at home around the clock, except for pre-approved activities such as work, school, or treatment. The most restrictive level—home detention—requires around-the-clock confinement at home, except for doctor's appointments, court appearances, and other activities exclusively authorized by the court. (Model Programs Guide, n.d.)

In the United States, the first EMD was developed in the mid-1960s by psychologist Robert Schwitzgebel, who believed his invention could deliver a humane and low-cost alternative to custody for many individuals entangled in the justice system. The device, known as the "Schwitzgebel Machine," consisted of a battery pack with a transmitter capable of sending a signal to a receiver within a range of approximately a quarter of a mile. Although Schwitzgebel obtained a patent for the device in 1969, the practical use of EMDs to monitor offenders did not begin in earnest until the 1980s. In the U.S., electronic monitoring grew rapidly, and by 1988 approximately 2,300 offenders in 32 states were being placed on electronic monitoring. Ten years later, the number of devices in use had leaped to more than 95,000 in January 1998—a fortyfold increase.

It is important to note that house arrest with electronic monitoring allows a person sentenced to jail to remain at home as an alternative to incarceration. In this arrangement, home confinement is closely monitored using an electronic sensor attached to the offender's ankle, connected through telephone lines to a central computer that receives a continuous signal. If the signal is broken because the offender travels beyond the authorized radius of the receiver, the host computer records the date and time of the signal's disappearance and its restoration. If a signal interruption occurs during a period when a parolee is required to be at home, the violation is confirmed by the Parole Officer, and the offender may be arrested. (Than, n.d.)

House Arrest as a Community Corrections Program

Among the most recent EMDs are devices based on GPS technology, which allow offenders to be monitored around the clock. In 1997, a new form of EM dependent on GPS was developed and tested. The GPS network is formed by 24 military satellites orbiting Earth; data from three to five of these satellites can establish the coordinates of a GPS receiver anywhere in the world. Through the GPS system, the whereabouts of EM clients can be determined and entered into central computers. Over the years, GPS systems have become easier to use and increasingly widespread.

The major distinction between a GPS system and a Radio Frequency (RF) EM system is the capacity to locate the movement details of clients. Through GPS, correctional authorities can determine when clients leave and return home, go to work, and attend mandatory treatment sessions. They can also identify whether clients have been visiting prohibited areas, such as the home of a victim, a workplace, a bar, or other establishments that serve alcohol. (Caputo, 2004)

Another important difference between RF-based EM systems and GPS is the ability to set exclusion zones and red-alert zones into which clients are prohibited from traveling. Because it is not strictly a punitive sanction, EM has been adapted for use in many contexts: it was devised as a post-trial supplement to home confinement and was readily adapted for pre-trial use as a means of releasing defendants on bail who might otherwise be considered too dangerous. It is useful for enforcing bail conditions such as avoiding victims or locations frequented by children. It is widely used as a community corrections alternative to jail or federal prison and as a means of increasing surveillance of parolees. It has also been applied as an intermediate sanction between increasing the number of contact meetings and revoking probation or parole, and is most commonly applied to work-release or temporary-release situations. (Caputo, 2004)

At times, criminal justice authorities may wish to control or closely monitor the movements of an individual without resorting to detention. For instance, prior to a criminal trial, police authorities might wish to guarantee that a defendant does not leave the city and stays away from the complainant. Following conviction, a judge might wish to restrict an offender's freedom without imposing a full-time custodial sanction. After release from jail, a parole board might wish to impose limits on an offender's behavior. Community-based programs seek to fulfill these objectives through release conditions such as reporting to officials or observing a curfew. EM enforces such conditions through technological means. Through the use of tracking systems, criminal justice agencies can monitor an individual's location and be alerted to any unlawful movements. (Black & Smith, n.d.)

History and Development of EMDs

There are three broad underlying principles behind the application of electronic monitoring:

(i) Detention: EM can be used to ensure that an individual remains at an assigned location. Home detention schemes, for example, typically require offenders to stay in their residence during curfew periods. This was one of the first uses of electronic monitoring and remains the most common.

(ii) Restriction: As an alternative measure, EM can be used to ensure that a person does not enter prohibited zones or come into contact with specific individuals such as complainants, potential victims, or co-offenders.

(iii) Surveillance: EM may be applied so that authorities can continuously track an individual without necessarily restricting their movements. (Black & Smith, n.d.)

There are three stages at which EM can be employed in the criminal justice system: pre-trial, during sentencing, and post-prison.

(i) Pre-trial: EM may be a condition upon which a defendant is granted bail. EM should thus be limited to surveillance unless detention is absolutely necessary. EM has been used as a pre-trial requirement in the U.S. Under one particular program, EM was available to those who were unable to pay the required bail amount. The program used a passive system, and if the accused attended trial after 90 days, the EM condition was lifted because the accused was thereafter considered low risk. (Black & Smith, n.d.)