Discretionary interventions initiated by the police, which aim to reduce subsequent offending by diverting individuals away from traditional criminal justice processes.
This summary is part of the Crime Reduction Toolkit, which presents the best available research evidence on what works to reduce crime.
Focus of the intervention
Police-led diversion programmes are discretionary interventions initiated by the police in response to individuals committing qualifying criminal offences. These interventions ‘divert’ individuals away from formal criminal justice processes – such as prosecution – towards non-criminal justice alternatives, with the aim of reducing subsequent offending.
Diversion can be initiated by the police at different stages of the pre-charge process, depending on the specific programme of intervention. Most commonly, alternative measures are offered or applied prior to individuals being arrested, at the point of their arrest or prior to them being charged.
Alternatives to formal criminal justice processing can include no further action, cautions, warnings, restorative justice measures and referrals to social, behavioural, educational or drug or alcohol treatment services.
This summary is based on one systematic review. The systematic review covers 47 studies evaluating programmes aimed at adults over the age of 18. Of the studies, 29 were from the USA, 10 from the UK, four from Australia, one from Ireland and three without location.
Effect – how effective is it?
There is some evidence that police-led diversion for adults has either increased or reduced offending, but as the review did not conduct a meta-analysis, no overall effect can be reported.
Across the 47 studies in the review, nine studies compared offending outcomes for treatment groups subject to diversion with those for comparison groups treated as usual. These studies were based on six quasi-experiments (three from the USA, two from the UK and one from Australia).
Of the nine studies, eight used rearrests to measure subsequent offending. Four out of the eight studies found that adults who were diverted by the police had lower rates of subsequent arrests than those who were processed in the criminal justice system. Three studies reported no statistically significant differences, and one found increased odds of re-arrest among diverted adults. One of the nine quasi-experimental studies used self-reported offending to measure subsequent offending and found no statistically significant differences between treatment and comparison groups.
In addition to the quasi-experimental studies, four descriptive and correlational studies found adults had fewer arrests and/or jail days in the period after they had been diverted compared to the period before.
How strong is the evidence?
Although the review was systematic, many forms of bias that could influence the study conclusions remain. The search strategy was well designed, transparent and provided some of the effect sizes for individual studies. However, it did not quantify an overall effect size across studies in accordance with meta-analytic techniques. In addition, it did not assess the validity of outcome constructs, sufficiently explore the influence of study design or provide an assessment of unanticipated outcomes from the effect.
Mechanism – how does it work?
The review suggested that police-initiated diversion for adults reduced subsequent offending through mechanisms such as identifying people who would benefit from treatment, referrals to behavioural health services and reducing stigma. However, these assumptions were not empirically tested in the review.
Moderators – in which contexts does it work best?
The review did not examine under what conditions or for what population groups the intervention might work best.
Implementation – what can be said about implementing this initiative?
The review gave no account of how the intervention was implemented, nor of any implementation challenges encountered by the primary studies.
Economic considerations – how much might it cost?
No formal economic analysis was provided in the review. However, some of the individual studies did report that police-initiated diversion programmes for adults were associated with reduced costs overall. Across all 47 studies, nine reported some economic information. Seven out of those nine studies reported cost savings when programme costs were taken into account, while two studies found no evidence of cost savings in relation to diversion. Of the seven that reported cost savings, four studies reported diversion saved ‘millions of dollars’, while two studies reported cost savings of more than US$1,000 per person diverted.
General considerations
- Only nine studies (out of 47) described within the systematic review reported results that could contribute to this summary.
- The timeframe covered in the studies is 2000 to 2018.
- Most evidence is taken from the USA, so caution should be taken when applying to other geographical contexts.
Summary
There is some evidence that police-initiated diversion programmes either increased or reduced crime. However, due to a lack of meta-analysis, no overall effect size can be reported.
Police-initiated diversion programmes are expected to reduce subsequent offending by diverting adults away from formal criminal justice processes – such as prosecution – towards a non-criminal justice alternative. However, despite the identification of some of the potential mechanisms for how police-initiated diversion programmes may work (e.g., stigma reduction and access to treatment), these were not empirically tested.
Although no formal economic analysis was carried out in the review, the review presented evidence from individual studies that police-initiated diversion for adults was associated with some cost savings. However, further research is needed to examine the implementation and economic outcomes surrounding police-initiated diversion programmes.
Reviews
Review one
Reference
Harmon-Darrow C, Afkinich J, Franke ND and Betz G. (2022). ‘Police Diversion at Arrest: A Systematic Review of the Literature’. Criminal Justice and Behavior, 50(3), pp 1-23, https://doi.org/10.1177/00938548221131965.
Additional resources
See also, police-initiated diversion for young people.