Imprisonment and other custodial sanctions
Evidence-rated crime-reduction intervention (EMMIE).
Effect on crime
increases crime
Evidence quality
strong
What the evidence says
This intervention discusses the use of custodial sanctions like imprisonment to punish lawbreakers and prevent future crime. The evidence suggests that such sanctions are associated with an overall increase in reoffending rates compared to non-custodial sanctions. Most evidence stems from a systematic review of 116 studies, predominantly from the USA, indicating that custodial sentences generally fail to deter crime effectively.
How it works
Custodial sanctions are based on the assumption that the threat of imprisonment will deter crime. However, this assumption is challenged by high rates of reoffending and the idea that custodial settings may expose individuals to risk factors that contribute to reoffending.
Implementation
The review did not provide specific details on the implementation of custodial or non-custodial sanctions, nor did it address potential challenges in implementation.
Source: College of Policing Crime Reduction Toolkit (What Works Centre for Crime Reduction). Summarised 2026-07-15. BlueLineHub is independent and not affiliated with the College of Policing.