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About the crime reduction toolkit and EMMIE framework

How the toolkit was created and how it measures the impact of policing and crime prevention interventions.

About the crime reduction toolkit

The crime reduction toolkit summarises the best available research evidence on what works to reduce crime. It uses the EMMIE framework (effect, mechanism, moderators, implementation and economic cost) to present evidence from systematic reviews.

The toolkit can be used by crime reduction practitioners and decision-makers. It allows you to assess the impact of different interventions on reducing crime and the strength of the evidence.

It also shows if there is information about:

  • how and where interventions work best
  • the implementation and economic cost

Systematic reviews

The toolkit contains systematic review level information for each intervention. 

A systematic review summarises the research evidence from multiple studies on a particular topic. It uses strict criteria to exclude studies that do not fit certain requirements for quality and methodology. 

Some systematic reviews include meta-analyses. Meta-analyses use statistical tests to estimate the overall effect of an intervention by combining data from multiple studies.


Evidence is presented using the EMMIE framework. EMMIE is a rating and ranking system that was developed by academics at University College London. It helps practitioners and decision-makers to access the evidence-base easily and quickly. EMMIE rates each intervention against five dimensions. 

  • Effect – impact on crime. Whether the evidence suggests the intervention led to an increase or decrease in crime, or had no impact.
  • Mechanism – how it works. What it is about the intervention that could explain its effect.
  • ​Moderators – where it works. ​The circumstances and contexts where the intervention is likely to work or not work.
  • ​Implementation – how to do it. The conditions that should be considered when implementing an intervention locally.
  • Economic cost – how much it costs. The direct or indirect costs associated with the intervention and any evidence of cost benefits.

Background on EMMIE

Copyright of the EMMIE framework is attributed to authors Professors Shane D. Johnson, Kate J. Bowers and Nick Tilley. 

The EMMIE framework was developed by UCL Jill Dando Institute as part of a programme of work designed to help build the toolkit 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 reference: ES/L007223/1.

The EMMIE framework is reproduced under the terms of the Creative Commons Attribution licence 4.0

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