Electronic tagging is a form of non-surreptitious surveillance consisting of an electronic device attached to a person or vehicle, especially certain criminals, allowing their whereabouts to be monitored. In general, devices locate themselves using GPS and report their position back to a control centre, for example via a cellular (mobile) phone network. This form of criminal sentencing, or increasingly a form of pre-release from detention monitoring, is known under different names in different countries; for example in New Zealand it is referred to as "home detention", and in North America as "electronic monitoring". Electronic monitoring has been said to be particularly useful for early detection of flight when defendants have been granted pretrial release, or for preparing incarcerated individuals for release back into the community. Increasingly, electronic tagging has become a tool for courts, penal institutions or hospital facilities, to manage individuals both within their facilities and external to their premises. Typical European usage of electronic tagging includes pre-trial and pre-release management of the person monitored. Use of tagging instead of incarceration reduces custody population and verifies that the person will obey conditions of release from custody.[original research?]
The same technology can be used for covert surveillance, particularly of vehicles, but would be called "tracking" rather than "tagging".
In 1964 Ralph Kirkland Schwitzgebel (family name later shortened to "Gable") headed a research team at Harvard that experimented with prototype electronic monitoring devices. In 1964 he 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, is housed at the Archives of the History of American Psychology, University of Akron, Akron, Ohio, USA.
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 October 6, 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. 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.
In the United Kingdom
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 hard wired 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.
A similar system is also in use in Belgium.
The monitoring of sex offenders via Electronic Tagging is currently in debate due to certain rights offenders have in England & Wales. 
Electronic tagging has begun being used on psychiatric patients, prompting concern from mental health advocates who state that the practice is demeaning. 
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 
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.
- Ankle monitor
- Automatic vehicle location
- Local Positioning Systems
- Global Positioning System
- GPS tracking
- Brazil awards the first GPS Monitoring of offenders contract to support early release programme
- BBC Article on tracking violent offenders due for release 18 August 2010
- Electronic Monitoring and Tracking using Local Positioning Systems
- Monitoring for abusive offenders and alcohol/drug abusers Ankle Bracelets – Ignition Interlock
- Tag 'too bulky' for bail woman at BBC News, 10 November 2005
- National Probation Service official website