Key findings

  • Studies have reported varying breach rates, often around 30 per cent, with breaches tending to happen earlier on. Many of those that breach subsequently complete their orders.
  • Findings on the impact upon reoffending have been mixed, with some positive effects found for sexual offenders and when used as an alternative to custody. Combining electronic monitoring with other interventions targeting offending-related needs has produced better results.
  • Home Detention Curfews have been found to be cost-effective compared to keeping people in custody.
  • Those tagged have expressed their preference for electronic monitoring compared to custody, but reservations have been expressed about the potential for long-term changes in behaviour. Tailoring to the individual is critical, with attention given to individuals’ circumstances and characteristics. It is important that those tagged can continue to provide care and support to significant others and that collateral damage to families and pro-social activities is minimised.
  • There is little evidence on the effectiveness of global positioning system enabled tags due to their recent rollout. Early findings indicate that care needs to be taken when defining and communicating boundary zones.


Electronic Monitoring (EM) is a blanket term used to describe a number of technologies deployed with a number of uses. It is provided via a worn device referred to as a personal identification device (PID) or more commonly a tag. The tag is designed to be hard to remove and is capable of providing evidence of tampering – the securing band is designed to snap under sufficient pressure as a safety measure but any intentional damage to the tag or tampering constitutes a major violation of the EM conditions.

EM is currently used in the following ways:

  • Curfew – a requirement added to a community sentence or as a licence condition at the point of release from custody. It specifies a time range that the individual must remain within their home – often a 12 hour period (typically 7pm until 7am) but can be for as long as 16 hours a day. Curfew requirements can be up to twelve months long. It is monitored with a radio frequency (RF) tag, linked to a base station within the home.
  • Home Detention Curfew (HDC) – a form of curfew used with those in the last months of a prison sentence. Suitable candidates are released early and must live at a designated address (typically their home) with a curfew, monitored with a RF tag. HDC numbers increased after changes in the eligibility rules in 2017.
  • Exclusion zone monitoring – a newer form of EM, only rolled out in 2019. It uses global positioning system (GPS) enabled tags to monitor an individual’s location and can raise an alert if the individual crosses into an excluded zone. The individual’s location is recorded at all times and can be made available to police to confirm locations at the time of an offence.
  • Sobriety tagging – a new form of tagging, initially piloted in Wales in 2020. It uses a specialised tag that can detect alcohol in small quantities in the perspiration from the skin of an individual and provides a way to detect whether the person tagged has been drinking alcohol. Its intended use is to monitor compliance with alcohol abstinence monitoring requirements (AAMR), typically used with those where alcohol consumption is a contributing factor in their offending behaviour, but who are not alcohol dependent.
  • Special uses – EM is also used in a variety of much more limited uses, such as with the small number of TACT (Terrorism Act) offenders who are often subject to GPS tagging, within intensive offender management (IOM) schemes, and with those taking compassionate release on temporary licence (ROTL).

The video below, produced by HM Prison and Probation Service, offers a quick guide to alcohol monitoring.

Disclaimer: an external platform has been used to host this video. Recommendations for further viewing may appear at the end of the video and are beyond our control.

Key statistics are as follows:

  • the number of people receiving a curfew requirement as part of a community order or suspended sentence order in the last year for which we have data (January 2020 to December 2020) was 14,845
  • releases on HDC have stayed between 26 and 29 per cent of eligible prisoners after a change in eligibility rules and process at the end of 2017. There were around 2,500 individuals on HDC in the community in the most recent monitoring period.

Summary of the evidence

Violations and breach rates

Studies have reported varying breach rates, often around 30 per cent. Not all breaches lead to revocation of the curfew, and many of those that breach have been found to subsequently complete their orders – completion rates around 80 per cent. Breaches have been found to be more common early in orders and less common when the curfew period is shorter than the maximum and when the curfew finishes earlier in the morning. Access to support is critical, providing information and reassurance to enable those tagged to complete their orders.

Studies on efficacy

A Swiss study found marginal better results for single order EM against single order unpaid work on reconviction and measures of social integration, the latter not support the hypothesis that more time confined at home worsens family relationships. A 2017 systematic review of 17 relevant studies found that EM had no statistically significant effect on reducing reoffending, except for sexual offenders and when EM was compared as an alternative to custody. This echoes findings from an earlier systematic review in 2012. Situational mechanisms (such as increased risk of getting caught) and behavioural mechanisms (such as encouraging pro-social behaviour) offer explanations as to how EM might reduce reoffending. The report also found that combining EM with other interventions such as therapy provided better results than EM alone. Economically, EM was found to be cheaper than prison but more expensive than ordinary probation/parole.

Studies into the efficacy of HDC have showed varying results from improvements in reoffending of 10 per cent in the most favourable studies to no improvement in the least favourable. While there is no consistent impact upon reoffending, none of the studies pointed to increases. Since HDC is much cheaper than keeping a person in custody, this suggests that HDC is relatively cost-effective.

Compliance rates within the two AAMR pilots were very high; 92 per cent and 94 per cent without breach, revocation or resentence. Wearers also reported improved family relationships and being healthier and happier as a result of their time on sobriety tags.

The experience of those tagged

A 2018 study found that the experiences of people ‘on tag’ varied, but most regarded EM favourably compared to a term in custody. Although there were potential benefits, these were not automatic, and further interventions targeting offending-related needs were required to get the maximum benefit. Those tagged mainly complied with the curfew due to fear of punishment and were less confident that their long-term outcomes and reoffending behaviour had really changed.

Tailoring to the individual has been reported as critical, with attention given to individuals’ circumstances and characteristics. Probation practitioners thus have a key role; through providing relevant information to the courts and prisons, it can be ensured that the use of EM is sufficiently tailored, proportionate and integrated. Research suggests that undertaking activities which create and/or strengthen social capital are important drivers for desistance. It is thus important that those tagged can continue to provide care and support to significant others and that collateral damage to families and pro-social activities is minimised.

GPS tagging

GPS tagging was only made available nationwide in 2019 and the uptake of cases for those on community orders and on licence has been relatively low to date. There have been reported difficulties in defining exclusion zones, and in communicating the details of the zones to individuals to enable them to comply. Flexibility is required in adapting exclusion zones to adapt to changing situations, such as a former victim moving house.

Both those tagged in the pilots and their responsible officers were positive about the ability to rule out involvement in criminal offences based on location monitoring.

Inspection data

We have twice examined EM provision through thematic inspection, in 2008 and 2012. These inspections looked at curfews both as requirements in community orders and as HDC. The 2008 inspection found that communication between courts, probation and EM providers was poor, particularly between courts and EM providers, with EM providers frequently getting information late from the courts or with missing or incorrect information.

In the 2012 inspection, it was found that curfews were often imposed without a pre-sentence report, even where probation held information that should have been considered, such as a history of domestic violence. In 2008, half of HDCs assessments had a home visit, but by the 2012 report, this had almost entirely ceased with assessments being conducted via a phone call to the resident instead. The judgement of the inspectors was that this process did not add any real value to the HDC process.

In both the 2008 and 2012 inspections, it was found that curfew requirements were not being integrated into sentence plans to help address offending behaviour.

Key references

Belur, J. Thornton, A. Tompson, L. Manning, M. Sidebottom, A. and Bowers, K. (2017). What works crime reduction systematic review series: No. 13 A systematic review of the effectiveness of the electronic monitoring of offenders. London: University College London.

Danielsson, P. and Mäkipää, L. (2012). A systematic literature review of electronic monitoring of offenders. Helsinki: National Research Institute of Legal Policy.

Fitzalan Howard, F. (2018). The experience of electronic monitoring and implications for practice: A qualitative research synthesis, HM Prison & Probation Service Analytical Summary. London: HM Prison & Probation Service.

Galisteo, S., Hillier, J., Liffen, E., Smith, H. and Stephenson, G. (2019). Process evaluation of Global Positioning System (GPS) electronic monitoring pilot: quantitative findings, Ministry of Justice Analytical Series. London: Ministry of Justice.

Graham, H. and McIvor, G. (2015). Scottish and International Review of the Uses of Electronic Monitoring. Stirling: Scottish Centre for Crime & Justice Research.

Hucklesby, A. and Holdsworth, E. (2016). Electronic Monitoring in England and Wales. Leeds: University of Leeds.

Hucklesby, A. and Holdsworth, E. (2020). Electronic Monitoring in probation practice, HM Inspectorate of Probation Academic Insights 2020/08. Manchester: HM Inspectorate of Probation. (PDF, 390 kB)

Kerr, J., Roberts, E., Davies, M. and Pullerits, M. (2019). Process evaluation of the Global Positioning System (GPS) electronic monitoring pilot: qualitiative findings, Ministry of Justice Analytical Series. London: Ministry of Justice.

Killias, M. Gillieron, G. Kissling, I. and Villettaz, P. (2010). ‘Community service versus electronic monitoring – What works better? Results of a Randomized Trial’, British Journal of Criminology, 50(6), pp. 1155-1170.

Nellis, M. (2016). ‘Electronic monitoring and Probation Practice’, in McNeill, F., Durnescu, I. and Butter, R. (eds.) Probation: 12 Essential Questions, London: Palgrave Macmillan, pp. 217-243.

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Last updated: 17 May 2021