This report presents the findings from a quasi-systematic review, or Rapid Evidence Assessment (REA), of the international literature in relation to knife crime. The research sought to address a range of questions relating to: how knife crime is measured and the difficulties associated with its measurement; who is involved in knife crime; and what interventions have been deployed to address this form of crime.

In order to provide a comprehensive picture of the available evidence in this area, a range of online databases and government websites were searched using a comprehensive list of research terms. Following de-duplication and recategorisation 171 unique journal articles and 19 government reports relating to knife crime were read. These papers and reports were analysed thematically to form the basis of the report. Key findings are set out below. Due to the tight timescale for the review, it is possible that some relevant evidence has not been referenced within the report, although it is assumed that all of the key studies have been included.

Measurement
It is important to be clear on what exactly is meant when using the term ‘knife crime’ as this has implications in terms of determining its prevalence. In particular, it is important to differentiate between two forms of behaviour that are often implicit in the term, namely, knife carrying and the use of knives in violent crime. This distinction between possession offences and violent crimes precipitated with a knife should be separated when we analyse data trends.

Official measures of knife crime can be divided into: (a) police-recorded data; (b) victimisation surveys; (c) self-report surveys; and (d) hospital admissions data. All of these sources have their own strengths and limitations and it may be that no one source adequately captures the ‘real’ levels of knife crime. In England and Wales, police statistics are regarded as a more reliable measure of knife crime than self-report or victimisation surveys, although these are often combined with data showing hospital admissions for assault with sharp weapons. Research suggests that when examining trends in knife crime looking at a number of datasets in the round can give the best indication of what might be happening on the ground. 

Risk Factors
Much of the research on knife crime has consistently identified a small number of motivations as important, namely, self-protection, self-presentation, and utility. In particular, research indicates that many young people report knife carrying (and weapon carrying more generally) because they are motivated to do so by the fear of victimisation. There is some evidence that the following factors may be associated with increased risk of violence and/or weapon carrying:
• Gender: men are much more likely to commit serious violence and carry knives;
• Age: young men are more likely to be involved in knife crime and there is a positive correlation in the literature between knife crime and adolescence;
• Substance abuse: substance use and binge drinking have been found to correlate strongly with weapon carrying, although the relationship is complex and it should not be assumed that they cause this behaviour;
• Mental health: multiple research papers have identified poor mental health and adverse childhood experiences (ACEs), such as abuse, neglect, parental criminality, as positively associated with knife crime;
• Victimisation: a significant number of studies have found that prior victimisation is positively correlated with weapon crime;
• School exclusion: UK research has shown school exclusion to be positively correlated with weapon carrying;
• Gangs: research suggests that knife crime should not be conflated with gang involvement;
• Community and societal factors: the research provides a strong case for knife crime being deeply rooted in wider social structures and relationships with peers and family, outside the immediate control of the individuals involved.

Research into the risk factors for victims of knife crime suggests considerable overlap with the risk factors for perpetration of knife crime, with the typical victim of knife crime also being a young male who may in turn go on to perpretrate knife crime. 

Interventions
The international evidence reviewed above suggests that a public health approach, involving multiple agencies to develop a range of interventions, including prevention work for at-risk groups, as well as law enforcement activity directed at offenders, represents the most promising approach to reducing knife crime. Promising interventions in a hospital setting have also been developed as part of the British Government’s Serious Violence Strategy. On the other hand, criminal justice interventions such as knife amnesties, stop and search and enhanced sentences present with limited crime reduction evidence. Evidence suggests that knife amnesties and stop and search will have a limited impact on violent behaviours using weapons and do not address the underlying causes of the behaviour. In particular, international evidence suggests that tougher penalties for knife crime have not had a deterrent effect on the carriage of knives and that increasing the rate of imprisonment merely increases reoffending on release. While promising, educational programmes in this area suffer from a lack of formal evaluations so that it is difficult to draw firm conclusions about their effectiveness.