The UK Home Office commissioned RAND Europe to systematically review the global literature in English, Dutch, Spanish and Portuguese on the impact of drug-related law enforcement activity on serious violence and homicide between 2011 and 2024. The research was commissioned to inform work the Home Office and other government departments undertook to implement the most recent Drugs Strategy ‘From Harm to Hope: a 10-year drugs plan to cut crime and save lives’, published under the 2019 to 2022 Johnson Conservative government (HM Government, 2021). Part of the Drugs Strategy related to stepping up the level of law enforcement on illicit drug-related activity.

This review addresses the following research question in the global literature: What is the impact of drug-related law enforcement activity on serious violence and homicide?

To explore this question, we examined 5 sub-questions:

1. Are certain types of drug-related law enforcement activity effective in reducing serious violence and homicide?
2. What aspects of drug-related law enforcement activity make them more/less likely to be effective in reducing serious violence and homicide?
3. Do certain types of drug-related law enforcement activity have unintended consequences, such as worsening adverse serious violence and homicide outcomes?
4. When drug-related law enforcement activity generates adverse serious violence and homicide outcomes, what are the factors that lead to these unintended consequences?
5. How do serious violence and homicide outcomes relating to drug-related law enforcement activity differ by country and local areas, and why?

This report reviews the evidence on 8 types of drug-related law enforcement activities (Chapter 3):

• selective enforcement for a specific area or group
• leadership removal
• attack or removal of a drug trafficking organisation member
• arrests or charges
• illegal crop eradication
• drug seizures
• military interventions
• multi-jurisdictional anti-drug coordination and resourcing

It also explores possible barriers to effectiveness and contributing factors that may help such activities reduce violence (Chapter 4). The report then analyses differences between and within countries regarding these interventions and their outcomes (Chapter 5).

The report concludes with reflections and implications from this review’s findings (Chapter 6), as follows:

Overall, the available evidence suggests that drug-related law enforcement activities are of limited effectiveness in reducing violence. Indeed, more studies demonstrated an association between drug-related law enforcement activities and increased violence than decreased violence. Selective enforcement tactics appeared the most promising in their capacity to reduce violence, although the evidence base covered in this review is limited.

Passive drug-related law enforcement activities, such as increasing police presence in known drug market areas, appear promising in reducing violence. However, less evidence is available on the effectiveness of these interventions than on active law enforcement activities.

The causal mechanisms of violence reduction are under-explored in the literature. However, several studies discussed supply disruptions, focused deterrence and positive relationships between police and communities as potential success factors.

Barriers to the effectiveness of violence-reduction efforts included the resilience of drug markets, the cultural significance of violence in some drug trafficking organisations, and law enforcement’s limited resources.

This review did not identify any UK-based evidence – most research came from the Americas. While most law enforcement activities in this review also occur in the UK, the results are not directly replicable in a UK setting.

Evidence on the relationship between drug-related law enforcement and serious violence and homicide over the last decade is lacking. What was previously effective (or ineffective) in reducing violence may yield different results now.

More evidence is needed on the effectiveness of drug-related law enforcement activities in retail-level markets or prison settings in reducing violence.

Relevant agencies planning and implementing drug-related law enforcement activity should consider the risk of increased violence, particularly for interventions for which available evidence suggests a strong association (for example, leadership removal and seizures).

Future UK research on drug-related law enforcement and violence could focus on interventions that may reduce violence, such as selective enforcement, and whether the findings presented can be validated.