About the Crime Reduction Toolkit


1.  What is the Crime Reduction Toolkit?

2.  What's in the Toolkit and how can it help me?

3.  What is a systematic review?

4.  What is the difference between the Toolkit in table mode and bubble mode?

5.  What is EMMIE?

6.  How do I interpret the impact of each intervention on crime reduction?

7.  What definitions are used for filtering? 

8.  Where can I find a comprehensive list of systematic reviews on crime reduction topics?

9. Who should I contact about using EMMIE?


What is 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 to present evidence from systematic reviews of research on crime reduction interventions in a format that helps users to access and understand it quickly.

What's in the Toolkit and how can it help me?
The Toolkit lists crime reduction interventions which span a broad range of approaches and problems.  It is not an exhaustive list of interventions used to reduce crime as the Toolkit only contains those that have been subject to at least one systematic review.  The systematic reviews are interpreted, rated and presented using a framework termed EMMIE (see below).  We continue to add interventions to the Toolkit when new systematic reviews measuring crime reduction are published.

The Toolkit can be used by crime reduction practitioners and decision-makers to help them to understand what works well (and what doesn't work) according to the best available evidence.  It allows them to assess different interventions in terms of their impact on reducing crime and the strength of the evidence.  Toolkit users can also clearly see if there is any information on how and where interventions work best and whether the research includes any information on implementation and economic cost. Clicking on the intervention title provides a summary of the findings, any noteworthy issues relating to the intervention, and access to the references for further reading. 

What is a systematic review?
A systematic review summarises the research evidence from a number of studies on a particular topic and uses strict criteria to exclude studies that do not fit certain quality and methodological requirements. Some systematic reviews include meta-analyses which use statistical tests to estimate the overall effect of an intervention by combining data from multiple studies. Only interventions that have been subject to a systematic review have been included on the Crime Reduction Toolkit.   

What is the difference between the Toolkit in table mode and bubble mode?
Both formats draw on the same research evidence relating to the same crime reduction interventions based on the EMMIE framework.  The main difference between the two modes is the way in which the evidence is presented.  Both modes allow you to access the evidence based on focus (prevention, diversion or reoffending), crime problem, population and other factors such as alcohol, drugs and gangs.

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

Effect​Impact on crime​Whether the evidence suggests the intervention led to an increase, decrease or had no impact on crime.
Mechanism​How it works​What is it about the intervention that could explain its effect?
Moderators​Where it works​In what circumstances and contexts is the intervention likely to work / not work?
Implementation​How to do it​What conditions should be considered when implementing an intervention locally?
Economic Cost​How much it costs​What direct or indirect costs are associated with the intervention and is there evidence of cost benefits?

Quick Start Guide to EMMIE
An introduction to EMMIE - the framework used to rate the best available evidence on crime reduction interventions - using Alley gating as an example.  To get started click on the Quick Start Guide below.


To find out more about EMMIE you can read the method statement. 

How do I interpret the impact of each intervention on crime reduction?
There are two steps to interpreting the impact of an intervention on crime.

    • The impact on crime effect scale shows you what the research evidence suggests about the effect of an intervention on reducing crime.  The scale ranges from interventions which show an overall decrease in crime ( ) to those  which show an overall increase () In some reviews, most studies showed an increase (or a decrease) in crime but a small number of studies within the review showed the opposite effect.  These are highlighted on the effect scale with a flag symbol ()
  • The quality scale (shaded bars beneath the effect scale symbols) shows you the quality of the research evidence. This ranges from no information (where we cannot comment on quality) to very good quality where we can feel confident in relying on the findings i.e. most forms of bias that could influence the study conclusions can be ruled out.

​Adult​Interventions that target adults and interventions where no reference is made to young people or children so it can be assumed the research relates to adults.
​Young person​Generally applied to interventions where population is above minimum school leaving age but may be younger than 18 years of age (eg applied to driving interventions to include newly qualified drivers).  Also applied to young adult populations sometimes described by reviewers as delinquents.
​Child​Applied to populations of under 18 years.  Sometimes applied in conjunction with young persons where the population is 17 and above.
​Location​Applied to interventions where a location e.g a car park or a residential street, is the target.
​Prevention​Interventions focussed on preventing crimes from taking place.  Includes situational prevention and people-based interventions.
​Diversion​Interventions targeting 'at risk' groups to divert them from committing crime.
​ReoffendingInterventions that deal with the offender after an offence has taken place to prevent repeat offending​.
​Factors​The factors filters (e.g alcohol, drugs, gangs) are applied to interventions that are explicitly linked to that particular factor.  Interventions can be linked to the factors by the focus of the intervention itself (e.g Policies related to alcohol sales - so are linked by 'alcohol') or by the outcomes the intervention has been tested against ( e.g the effectiveness of youth curfews has been tested specifically on gang-related crime).

Some interventions in the Toolkit may also be effective at tackling factors related to crime, but if they have not been explicitly linked to such factors, the filter has not been applied.

Factor filters are always applied to Problem Oriented Policing (POP). POP is a problem solving approach to develop targeted interventions rather than an intervention per se.  Therefore a POP approach can be applied to any crime and disorder problem.


Where can I find a comprehensive list of systematic reviews on crime reduction topics? 
This database is the result of a systematic search for all systematic reviews and/or meta-analyses with a crime reduction focus. 324 reviews are included in these data (duplicates and linked documents have been removed). Please note that each research records spans multiple lines due to restrictions incurred when exporting the database from the reference management software (EPPI Reviewer-4).

The initial search carried out by UCL to identify systematic reviews which included a crime reduction measure identified this list, some of which were excluded from the Crime Reduction Toolkit because they did not meet our criteria.  

Who should I contact about using EMMIE?
Copyright of the EMMIE Framework is attributed to authors; Professors Shane D. Johnson, Kate J. Bowers and Nick Tilley. 

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

The following academic paper on EMMIE was published in the Journal of Experimental Criminology.
Johnson, S. D., Tilley, N., & Bowers, K. J. (2015). Introducing EMMIE: An evidence rating scale to encourage mixed-method crime prevention synthesis reviews. Journal of Experimental Criminology, 11(3), 459-473.

All correspondence regarding the use of EMMIE should be directed to Shane D. Johnson.

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 Ref: ES/L007223/1.

The Crime Reduction Toolkit has been awarded a Best Practice certificate in the European and National Level category at the European Public Sector Awards 2017

If you have any questions about the Crime Reduction Toolkit, please email whatworks@college.pnn.police.uk

© College of Policing Ltd (2020).  All Rights Reserved.  No part of the Crime Reduction Toolkit may be reproduced, modified, amended, stored in any retrieval system or transmitted, in any form or by any means, without the prior written permission of the College unless expressly permitted by law.  Anyone wishing to copy or re-use all or part of the Crime Reduction Toolkit for purposes other than expressly permitted by law will need a licence.  Licence applications can be sent to the Copyright and Licensing team by email: Copyright&Licensing@college.pnn.police.uk