A systematic review of the effectiveness of the electronic monitoring of offenders

Objective: This paper reports the findings of a systematic review on the effectiveness of Electronic Monitoring (EM) on reducing recidivism. It identifies mechanisms through which EM is expected to produce reductions in recidivism rates, under what conditions, and at what cost. Methods: Eligible studies were identified through a search strategy and quality appraised. The review uniquely combines findings of a meta-analysis alongside a realist-inspired qualitative synthesis. Results: 34 studies met our inclusion criteria. Meta-analytic results from 18 studies found that although overall the effect of EM on recidivism was favourable, heterogeneity between studies meant that the effect was significant for studies using hazard ratios but non-significant for those using proportional data. Findings indicated statistically significant reductions in recidivism for sex offenders; when EM is compared to the alternative of prison; and in European settings. Situational and behavioural mechanisms that might plausibly reduce recidivism were identified. EM is cheaper than prison but more expensive than ordinary probation or parole. Conclusions: The study illustrates the complexity of implementing EM. We present a theory of change for EM in the form of logic models and discuss the implications of the interaction between identified factors on implementation of EM to achieve desired outcomes.