Electronic monitoring (EM) is used for a variety of purposes but is often employed as an alternative or follow-up to imprisonment. It involves an offender wearing an ankle bracelet or similar device that monitors their whereabouts. It has been used with offenders who have committed a variety of offences and with offenders believed to pose different levels of risk to society. This summary concerns the effect of EM on moderate to high-risk offenders.
This narrative is primarily based on one systematic review covering three studies.
There is some evidence that the intervention has reduced crime, but overall the intervention has not had a statistically significant effect on crime.
Across the three studies reviewed, the rate of re-imprisonment was found to be similar for offenders who were subject to EM and a sample of offenders (with similar characteristics) who were not. However, it is worth noting that this conclusion is based on the analysis of follow-up data, which continued after the EM had been removed.
The results of one study that examined different periods of time suggest that it is possible that EM is effective while it is in use and shortly afterwards, but not in the longer-term.
There was no evidence of a backfire effect (where crime increased).
This evidence is taken from a systematic review covering just three studies (conducted in Canada, America and the UK). Although the review was systematic, some forms of bias that could influence the study conclusions remain.
The review had a transparent and well-designed search strategy, but the small number of studies included is a concern. Many low quality evaluation studies on EM were excluded from the review. The follow-up periods varied across the three studies (from one to three years) and extended beyond the period that EM was used, which is questionable. None of the studies used a random allocation strategy, or other procedures to assign offenders to conditions. Consequently, the EM and control groups may have differed in ways other than the use of EM.
The review does not discuss the mechanisms involved, but implies that if EM did work it would do so by increasing deterrence and/or reducing opportunities for offending. However, no effort was made to explicitly state or empirically test any mechanisms in the review.
EM may be effective for sex offenders. However, where EM appeared to be effective, this could have been the result of other factors, as EM was often employed in combination with other interventions and/or measures that were not always adopted in the control groups.
No implementation-related information was provided for the three studies included in the review. One implementation issue highlighted from an excluded study was that some 56% of offenders were never actually monitored electronically.
The review does not mention costs (and/or benefits) and no formal economic analysis is provided.
Researchers elsewhere have attempted to quantify the costs, benefits or cost effectiveness of the intervention. For example Haverkamp, Mayer, & Lévy (2004) reported that electronic monitoring cost €50 per offender, per day, in England at the time of their study. In some places offenders absorb some of the costs – for example, in Pennsylvania, USA Courtright, Berg, & Mutchnic (1997) note that offenders were charged a daily fee (US$ 8) for the electronic monitoring equipment and a monthly fee for regular supervision (US$ 25). Whether electronic monitoring is cost-effective or not depends upon alternative sentencing options. Several economic calculations assume that a corresponding imprisonment period would be more expensive, and so electronic monitoring is seen as cost-beneficial (Courtright et al, 1997 report a ratio of 4.02:1). This remains the case even if no reduction in re-offending is observed.
In contrast, if electronic monitoring is combined with standard probation service disposal – and compared with probationer without EM - it is inevitably going to cost more. Some research reports that the benefits outweigh this additional cost (Glaser, & Watts, 1992), however, in light of the often-observed questionable effects of EM, this must be interpreted with caution.
A recent estimate of the cost of implementation was produced by the Washington State Institute for Public Policy specifically for Washington State. The estimate was $1,102 in 2013 dollars.
The sample size for this review (three studies) is inadequate for reliable conclusions to be drawn.
The follow-up periods over which recidivism was measured varied across the three studies reviewed, from one to three years. Although the same follow-up period was employed for both EM and control offenders within each study, it is questionable whether the recidivism rates should have been aggregated across studies (as the different follow-up periods might make them non-comparable).
Future studies should aim to conduct high-quality evaluations that differentiate between monitoring and post-monitoring periods, control for other interventions/measures in place, and aim to test the mechanisms that are thought to make EM work.
If more primary evaluation studies are conducted, it would be helpful to differentiate between different forms of EM, such as continuous signalling (CS) and random calling (RC), as the type of EM may affect the underlying mechanisms and its general effectiveness.
Overall evidence suggests that Electronic Monitoring (EM) has no impact on crime (but some studies suggest a decrease). EM is usually combined with other interventions aimed at desistence from crime, and evaluation studies often examine the effectiveness of EM for a period of time that extends beyond the monitoring period. This makes the interpretation of the impact of EM difficult. There is a sizeable gap in the evidence base, which requires more carefully designed studies.
Renzema, M. & Mayo-Wilson, E. (2005). Can electronic monitoring reduce crime for moderate to high-risk offenders? Journal of Experimental Criminology, 1(2), 215-237.
Courtright, K., Berg, B.L., & Mutchnick, R.J. (1997). The cost-effectiveness of using house arrest with electronic monitoring for drunk drivers.
Federal Probation, 61,445-446.
Glaser, D., & Watts, R. (1992). Electronic monitoring of drug offenders on probation.
Judicature, 7 (3).
Haverkamp, R., Mayer, M., & Lévy, R. (2004). Electronic Monitoring in Europe.
European Journal of Crime, Criminal Law and Criminal Justice, 12(1), 36-45.
This narrative was prepared by UCL Jill Dando Institute and was co-funded by the College of Policing and the Economic and Social Research Council (ESRC). ESRC Grant title: 'University Consortium for Evidence-Based Crime Reduction'. Grant Ref: ES/L007223/1.
Uploaded on 19/02/15