Electronic tagging

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Electronic tagging is a form of surveillance consisting of an electronic device, usually attached to a person, by law enforcement, capable of tracking the wearer's location, transmitting information about his activities, communicating with him, and perhaps modifying his behaviour.[1]

The device is commonly associated with paroled sex offenders-- or any of a variety of other lawbreakers, including killers, thieves, and drug users-- who wear it so authorities can keep an eye on their movements.[2] In a similar application, electronic monitoring devices are used to confine offenders to their homes as a condition of early release from prison. In fact, electronic monitoring is an extended control and surveillance of the offender from prison to the community--"prisons in the home" or "the electronic ball and chain."[3]


Conceptual history[edit]

The use of home detention as a means of confinement and control within the home can be traced back to biblical times when the Romans placed Paul the Apostle, under house arrest.

In the 18th century, the English philosopher and social theorist Jeremy Bentham designed the Panopticon, a hypothetical prison. Inside the Panopticon (the name is derived from the Greek word for “all-seeing”), the prisoners are arranged in a ring of cells surrounding their guard, who is concealed in a tower in the center. The idea is that the guard controls the prisoners through his presumed observation: they constantly imagine his eyes on them, even when he’s looking elsewhere.

"[T]he persons to be inspected should always feel themselves as if under inspection ... for the greatest proportion of time possible, each man should actually be under inspection."

Bentham promoted the concept of the Panopticon for much the same reasons that spur criminal-justice innovation today—a ballooning prison population and the need for a cheap solution with light manpower demands. It is worth remembering that when the modern prison emerged, it, too, was promoted as a reform a positive replacement for corporal or capital punishment. Early prison reformers—many of them Quakers bent on repentance and redemption—suggested that cutting people off from the rest of the world would bring them closer to God. (The word "penitentiary" comes, of course, from "penitence.") Whereas the guard in Bentham’s day had only two eyes, however, today’s watcher can be virtually all-seeing, thanks to GPS monitoring technology. The modern prisoner, in other words, need not wonder whether he is being observed; he can be sure that he is, and at all times.


The technologies of electronic monitoring have their roots in the work of Dr. Ralph Schwitzgebel of the Science Committee on Psychological Experimentation at Harvard University (1968). In 1964, Ralph Kirkland Schwitzgebel (family name later shortened to "Gable") headed a research team that experimented with prototype electronic monitoring devices. Schwitzgebel and William S. Hurd were granted patent #3,478,344 and published an article informing how such monitoring devices could be used.

In 1969, Robert Schwitzgebel ("Gable"), a professor at UCLA and Claremont Graduate University in California, wrote an article in Psychology Today about an FCC-licensed experimental radio station to locate and send two-way radio signals to juvenile offenders. A collection of tagging devices used in the United States between 1970 and 1990, and a summary of their early history, with photographs,[4] is housed at the Archives of the History of American Psychology, University of Akron, Akron, Ohio, USA. developed a one-kilogram Radio Telemetry Device that could be worn by a person. The device transmitted signals to a modified missile-tracking unit up to 400 metres away, which determined the wearer’s location on a screen. The Harvard researchers invented and assessed a prototype monitoring system to use upon juvenile offenders. The public responded unfavorably on the whole, fearing that the devices were overly intrusive. Twenty years later, in 1983, a New Mexico district court judge first sentenced offenders to electronic monitoring by home. Even in 1966 it was noted that, in theory, the system could be modified to gather and transmit physiological data such as pulse rates, blood alcohol levels, brain waves, or information on other bodily functions of the wearer and, conversely, that information or stimulation could be sent back to the person wearing the transmitting device. It could also be easily adapted to serve as a listening device or two-way radio. The system was tested on volunteers who included students, parolees and mental patients, and experiments along these lines exploring its possibilities were conducted.

Schwitzgebel was granted a patent in relation to the system in 1969.

A diversion from the EM’s criminal justice application, in 1978, BI Incorporated began selling systems that allowed dairy farmers to dispense feed to their cows automatically. The company fitted a radio-frequency tag on each cow’s ear so that when the cow approached the feed dispenser, a sensor in the latter caused it to drop a ration of fodder. If the same cow returned, the sensor recognized the unique signal of the tag and prevented the cow from getting a second helping until after enough time had passed for her to digest the first.

Appropriately enough, electronic monitoring was introduced in 1984. In fact, though seldom thought of this way, the ankle monitor is essentially a constant, warrantless search.

In 1981 writer Tom Stacey took to the British Home Office a proposal for the electronic tagging of offenders to track their movements, or fix a home curfew, using cellular radio telephone technology. Stacey had been briefly imprisoned abroad in his former role as a foreign correspondent and had for several years served as a Prison Visitor in England. He followed his presentation to the Home Office with a letter to The Times (published 6 October 1982) outlining the proposal and his immediate formation of the Offender's Tag Association, composed of electronic scientists, penologists and prominent citizens. The term 'tagging' thus entered the vocabulary in the penal context. In March 1983 the Offender's Tag Association held a national press conference. Later that year, a district court judge, Jack Love, persuaded Michael Goss, a computer salesperson, to develop a system to monitor five offenders in Albuquerque, New Mexico. Judge Love was supposedly inspired to act based upon a storyline in a Spider-Man comic, specifically the newspaper comic strip version where the Kingpin puts an electronic bracelet on the superhero primarily to follow his movements.[5] This was probably the first court-sanctioned use of electronic monitoring.

Until the widespread adoption of cellular and broadband internet networks in the mid-1990s, electronic monitoring devices were typically home-based, dependent on a dedicated land line, and able to report only whether or not the criminal being tracked was remaining at home. This was useful for criminals on work-release, parole, or probation, for example DWI offenders who were allowed to leave home to go to work during daytime hours but had to return home and remain there after a certain time of the evening. More recent technology such as GPS and cellular networks have permitted courts to order more specific restrictions, such as permitting a registered child sex offender to leave his home at any time of day, but alerting authorities if they come within 100 metres of a school, park, or playground.

How it works[edit]

Big picture[edit]

3-Dimension Trilateration[edit]

Imagine you are somewhere in the United States and you are TOTALLY lost. You ask for directions. A local tells you: “you are 625 miles from Boise, Idaho. You could be anywhere on a circle around Boise that has a radius of 625 miles, like this:

You ask somebody else where you are, and she says, "You are 690 miles from Minneapolis, Minnesota." If you combine this information with the Boise information, you have two circles that intersect. You now know that you must be at one of these two intersection points, if you are 625 miles from Boise and 690 miles from Minneapolis.

If a third person tells you that you are 615 miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points.

This same concept works in three-dimensional space, as well, where you're dealing with spheres instead of circles.

3-Dimension Trilateration[edit]

Artist's impression of a Navstar-2F satellite in orbit.

If you know you are 10 miles from satellite A in the sky, you could be anywhere on the surface of a huge, imaginary sphere with a 10-mile radius. If you also know you are 15 miles from satellite B, you can overlap the first sphere with another, larger sphere. ... If you know the distance to a third satellite, you get a third sphere, which intersects with this circle at two points.

The Earth itself can act as a fourth sphere -- only one of the two possible points will actually be on the surface of the planet, so you can eliminate the one in space.

The GPS receiver figures both of these things out by analyzing high-frequency, low-power radio signals from the GPS satellites. Radio waves are electromagnetic energy, which means they travel at the speed of light (about 186,000 miles per second, 300,000 km per second in a vacuum). The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive.

...The correct time value will cause all of the signals that the receiver is receiving to align at a single point in space. ... So the receiver sets its clock to that time value, and it then has the same time value that all the atomic clocks in all of the satellites have.

...When you measure the distance to four located satellites, you can draw four spheres that all intersect at one point. Three spheres will intersect even if your numbers are way off, but four spheres will not intersect at one point if you've measured incorrectly.

...The receiver does this constantly whenever it's on, which means it is nearly as accurate as the expensive atomic clocks in the satellites.

In order for the distance information to be of any use, the receiver also has to know where the satellites actually are. ... Things like the pull of the moon and the sun do change the satellites' orbits very slightly, but the Department of Defense constantly monitors their exact positions and transmits any adjustments to all GPS receivers as part of the satellites' signals.

For one thing, this method assumes the radio signals will make their way through the atmosphere at a consistent speed (the speed of light). Problems can also occur when radio signals bounce off large objects, such as skyscrapers, giving a receiver the impression that a satellite is farther away than it actually is.

The station then broadcasts a radio signal to all DGPS-equipped receivers in the area, providing signal correction information for that area.

The most essential function of a GPS receiver is to pick up the transmissions of at least four satellites and combine the information in those transmissions with information in an electronic almanac, all in order to figure out the receiver's position on Earth.

Once the receiver makes this calculation, it can tell you the latitude, longitude and altitude (or some similar measurement) of its current position.

You can use maps stored in the receiver's memory, connect the receiver to a computer that can hold more detailed maps in its memory, or simply buy a detailed map of your area and find your way using the receiver's latitude and longitude readouts.

A standard GPS receiver will not only place you on a map at any particular location, but will also trace your path across a map as you move. If you leave your receiver on, it can stay in constant communication with GPS satellites to see how your location is changing.

The device would enable the monitoring company to follow his every move, from home to work to the store, and, in consultation with a parole or probation officer, to keep him away from kindergartens, playgrounds, and other places where kids congregate. Should he decide to snip off the anklet (the band is rubber, and would succumb easily to pruning shears), a severed cable would alert the company that he had tampered with the unit, and absent a very good excuse he would likely be sent back to prison.

Small picture[edit]

The portable device is operatively coupled to a monitoring system through a wireless telephone network. The portable device transmits periodically encrypted location information as well as status information across the wireless network to the monitoring system. The monitoring system tracks the location of the individual and alerts the appropriate authorities when the individual violates a rule, such as a condition for parole. The portable device increases the time between transmissions when the individual is within a specified home location and reduces the time between transmissions when outside the specified location.

As a fail-safe against any technological glitch, whether accidental or malicious, a leading Electronic Monitoring operator is immensely proud of its backup systems, which boast an ultrasecure data room and extreme redundancy: if, say, a toxic-gas cloud were to wipe out the town of Anderson, the last act of the staff there would be to flip the switches diverting all call traffic to BI’s corporate office in Boulder, Colorado, where a team capable of taking over instantly in case of disaster is always on duty.

Other designs[edit]

Commercial use[edit]

In the late seventies and early eighties, many stores began to install closed-circuit cameras and electronic-article-surveillance technology—known as E.A.S. E.A.S. tags, which can be sewn into garments or slipped between the pages of books, contain a small magnetic coil that triggers an alarm at store exits. The technology is still in wide use despite its questionable effectiveness. The problem is not only that false alarms are so frequent (who hasn’t set off an alarm at a store exit and been waved through by a weary security guard?), or that thieves have learned to defeat the system with foil-lined booster bags, but that the alarm sounds only after a thief has passed through the security gates.

Among other things, its signals are used to synchronise the clocks in mobile-phone base stations, steer combine harvesters and keep oil platforms in position.

Parental use[edit]

A company in Japan created GPS enabled uniforms and backpacks. School children, in distress, would be able to hit a button, immediately summoning a security agent to their location. Other similar applications have included mobile phones, in America, enabled with GPS tracking to allow parents track their school children.

Vehicular use[edit]

Public transit vehicles are outfitted with electronic monitoring devices that talk to GPS systems tracking their locations. App developers have integrated this technology with mobile-phone apps. Now, passengers are able to receive accurate public transit timetables. Another application is

Medical/Health use[edit]

GPS-based systems have been created to help stave off the anxiety of monitoring the locations of Alzheimer's patients. Alerts are sent to family members if the patient leaves the designated zone.

Apple’s iOS uses Location Services allows location-based apps (particularly health and fitness apps) to use information from (GPS)2 networks, to determine your approximate location. Depending on your device and available services, Location Services uses a combination of cellular, Wi-Fi, Bluetooth, and GPS to determine your location. If you're not within a clear line of sight to GPS satellites, your device can determine your location using crowd-sourced Wi-Fi5 and cell tower locations or iBeacons For example, an app might use your location data and location search query to help you find nearby coffee shops or theaters, or your device may set its time zone automatically based on your current location.


A major advantage is the possibility of reduced prison populations. This is most likely where monitoring is used as an alternative to prison, rather than to enhance existing non-custodial orders. Major cost savings may be achieved through building fewer prisons as well as reducing the cost of administering custodial sentences.

Another is the possibility of improving rehabilitation and reintegration of offenders. Electronic monitoring may allow more offenders to maintain employment and contact with their families. It also avoids any negative psychological effects of incarceration, although of course the wearing of a device carries its own psychological pressures.


A disadvantage of electronic monitoring is the lack of incapacitation. Electronic monitoring does not physically restrain a person and dangerous offenders are still able to offend before authorities can intervene. Also, the less onerous conditions of home detention with electronic monitoring may result in some victims and the public perceiving some offenders as being treated leniently.

According to an analysis in the Journal of Law and Policy, most of those placed on electronic monitors haven't committed serious or violent offenses and, were it not for monitoring, "at least some of these populations would not in fact be incarcerated or otherwise under physical control."

Eighty-nine percent of probation officers surveyed by the Justice Department felt that "offenders' relationships with their significant others changed because of being monitored." Both officers and those monitored observed that the ankle band had a distinct impact on children. As one parent testified, "When it beeps, the kids worry about whether the probation officer is coming to take me to jail. The kids run for it when it beeps."

It took two months for investigators from the Federal Aviation Authority to track down the problem. In late 2009 satellite-positioning receivers for a new navigation aid at Newark airport in New Jersey were suffering brief daily breaks in reception. Something was interfering with the signals from orbiting global positioning system (GPS) satellites. A driver who passed by on the nearby New Jersey Turnpike each day used a cheap GPS jammer in his truck. Jammers prevent tracking devices from determining (and then reporting) its location. Everything from aviation, financial-securities clearing, mining and electricity distribution to mobile telecoms, road tolling and weather forecasting rely on GPS. All of them share a fundamental weakness, however. Because they rely on signals from satellites transmitting from an altitude of around 20,000 kilometres (12,400 miles), the signals are very weak, making them vulnerable to accidental or deliberate interference. This can take the form of natural interference, as a result of solar activity, for example; accidental man-made interference due to signal reflection or faulty transmitter equipment; and deliberate jamming of the satellite signal by transmitters that drown it out by broadcasting their own signal on the same frequency

Literature and the arts[edit]

As a condition for her bail, Gabrielle Baillieux, the protagonist in Peter Carey’s Amnesia had to wear an ankle monitor. Later a colleague soldered it off. The device was transferred to a dog, whose movements were instead tracked.

The Good wife, (“Bang”) season 1 episode 15 Peter had been imprisoned for several months after being convicted of charges of corruption. He is allowed to return home under house arrest while his appeal is considered. Peter must wear an ankle monitor and cannot leave the apartment or communicate with the outside world.

Notable instances[edit]

Lindsay Lohan: failed to appear at a mandatory hearing, and a warrant was issued for her arrest. The judge ordered Lohan to wear a SCRAM bracelet, an electronic device that monitors the bloodstream for alcohol and drugs and alerts authorities if prohibited substances are consumed.

Roman Polanski one of the most famous fugitives from American justice in the world was finally arrested in Switzerland. The terms of his release included $4.5m bail, house arrest wearing an ankle bracelet at his chalet, known as Milky Way, in the Swiss ski resort of Gstaad, after having spent sixty-seven days in a Zurich detention centre.

Bernard Madoff the financier accused in a $50 billion fraud case before trial was ordered under house arrest, with electronic monitoring, and posting $10 million bail against his $7 million Manhattan apartment, and against his wife's homes in Montauk, N.Y., and Palm Beach, Fla.

Dominique Strauss-Kahn, Former International Monetary Fund chief, charged with trying to rape a hotel maid May 14 2011. On release from jail, arranged for house arrest, with a private security company that kept him under armed guard and electronic monitoring as conditions of his bail. Prosecutors estimated the cost at $200,000 a month, which he was responsible for paying.

Dr. Dre In 1992, the rapper was arrested for assaulting record producer Damon Thomas and later plead guilty to assault on a police officer, eventually serving house arrest and wearing a police-monitoring ankle bracelet.



The US correctional system is overwhelmed by the over-incarceration of Nonviolent offenders such as drug users. Private-prison corporations themselves have begun to expand into the “alternatives” industry. The GEO Group now has an array of “community reëntry services” and treatment programs. In 2011, it acquired the country’s largest electronic-monitoring firm, BI Incorporated, for four hundred and fifteen million dollars. For the most part, these companies deal not with felony probationers—“probation” as it’s usually understood—but with people whose offenses are often too minor to merit jail time. The system is known as “offender-funded” justice.

Jack Long, a Georgia attorney filed a habeas petition on behalf of a client who, after stealing a two-dollar can of beer from a convenience store, was ordered to spend a year wearing an ankle bracelet operated by a company called Sentinel Offender Services. The man wound up owing more than a thousand dollars to the company in fees and late-payment penalties, and started selling his blood plasma to keep pace. Dozens of probationers are jailed because of electronic-monitoring bills, most of which, were not authorized by any legal statute.


Electronic monitoring of a curfew has become an integral part of the criminal justice system, used at various stages of criminal cases. Since electronically monitored curfews were rolled out throughout England and Wales their use has increased sharply, from 9,000 cases in 1999-00 to 53,000 in 2004-05. In 2004-05, the Home Office spent £102.3 million on the electronic monitoring of curfews. Electronic monitoring is used to monitor compliance with a curfew, requiring the curfewee to remain in their home for a specified number of hours a day.4 Typically, offenders are fitted with an electronic tag around their ankle which sends a regular signal to a receiver unit installed in their home. Electronically monitored curfews are considerably cheaper than custody. Ninety days in custody costs nearly five times as much as 90 days on Home Detention Curfew or Adult Curfew Order.

A simpler form is in regular use in the United Kingdom, where a base station is connected to the mains supply at the offender's home, and a tag is attached to the offender's ankle. If the tag isn't functioning and within range of the base during curfew hours, or if the base is disconnected from the power supply, then the authorities are automatically alerted. Some systems are connected to a fixed telephone line, whilst more modern systems utilise a mobile phone/cellular system to communicate with the authorities. The system can also be used to enforce restrictions away from specified locations such as victims' homes, and football grounds. Instead of allowing full location tracking, this system can be used to enforce the curfews which commonly form part of community-based sentences, the conditions of Home Detention Curfew or parole of offenders released from prison. Most of these uses are now covered by the Criminal Justice Act 2003 in England and Wales, with separate legislation applying in Scotland. The system is also used for monitoring those subject to house arrest or other "Control orders" under the Prevention of Terrorism Act 2005.

The monitoring of sex offenders via electronic tagging is currently in debate due to certain rights offenders have in England and Wales.[6]

Electronic tagging has begun being used on psychiatric patients, prompting concern from mental health advocates who state that the practice is demeaning. [7]

South Africa[edit]

Electronic monitoring as a pilot project was started in March 2012, involving 150 offenders, mostly prisoners serving life terms. The project was rolled out to reduce the South Africa’s prison population. It consequently would also reduce the taxpayer’s burden on correctional facilities. South Africa locks up more people than any other country on the continent.



A similar system is also in use in Belgium.


In August 2010 Brazil awarded a GPS Offender Monitoring contract to kick start its monitoring of offenders and management of the Brazilian governments early release programme [8]

The device[edit]

The current UK G4S administered ankle device is made up of a black band, approximately 2.5 cm in width, with an 8 cm long x 3 cm wide grey 'heart'. Along the length of the black strap at the edges run 2 length of fibres which only appear to add strength to the black strap. Additionally, and presumably to record any deliberate cutting of the strap, runs what appears to be a 10-or-so core fibre optic cable which pulses roughly every 1/2 second. Each ankle device has a serial number and a telephone number imprinted on it, should one need to contact the control room.[citation needed]

See also[edit]


  1. ^ "Anthropotelemetry: Dr Schwitzgebel's Machine". Harvard Law Review (80): 403. 1966. 
  2. ^ Wood, Graeme. "Prison Without Walls". The Atlantic Monthly. 
  3. ^ Gibbs, Anita; King, Denise. "The electronic ball and chain? The operation and impact of home detention with electronic monitoring in New Zealand". AUSTLNZJCRIM 1 2003 WLNR 17615940. 
  4. ^ Robert S. Gable, An Informal History of the Beginning of Electronic Monitoring of Offenders, 8 December 2009
  5. ^ QI Transcript, Season 4 Episode 8 QI, Transcript on qitranscripts.com; Broadcast 2006; Accessed 25 September 2007
  6. ^ Electronic tagging of offenders raises rights concerns, The Guardian, 12 August 2010
  7. ^ GPS tracking mental health patients - human rights concerns, BMH UK, 22 June 2010
  8. ^ SecureAlert Signs First-Ever GPS Offender Monitoring Contract in Brazil, TMCnet, 23 August 2010

External links[edit]