A major study examined over 62,000 drug-related cases handled by 13 English police forces over four years. The finding: when police offer alternatives to prosecution for drug offenses — like treatment referrals instead of court charges — people are less likely to reoffend.

But there is a catch. How well the program is actually run matters more than almost anything else. When officers apply the rules inconsistently or skip steps, the benefits shrink.

What the Research Found

This study used a method called "realist evaluation." Instead of just asking "does this work?" researchers asked "what works, for whom, and under what conditions?" That matters because "drug diversion" is not one thing. It includes everything from a simple cannabis warning, to conditional cautions, to being referred to drug treatment or education classes. Lumping these together hid important differences — which is why earlier research often missed the real picture.

The headline result — fewer people reoffending — matches what other independent researchers found at UCL and reported by other teams. When researchers working separately reach the same conclusion, that is a stronger signal the finding is real.

What stands out is implementation fidelity. Think of it like following a recipe: if police officers are not carrying out the program as designed — skipping referral steps, applying rules differently depending on the person — the program stops working well. Smaller research projects could not catch this clearly, but the scale of this 13-force study makes it unmissable.

The Hidden Problem

There is a serious structural issue running beneath this good news. In 2021, the police inspectorate found that nearly one in five stop-and-search operations for drugs had no proper legal grounds. That is important because if the police stop and search someone unlawfully in the first place, what happens after is tainted from the start.

This is not just a legal technicality. If diversion programs are built on stops that should never have happened, people — especially those already over-policed — lose trust in the whole system. The program is meant to help, but it starts with a breach.

Young People Face Special Risks

Research from Kent shows that when young people get formally charged with a crime, they are more likely to reoffend later. A formal charge creates a label — criminal record, employment barriers, housing trouble — that pulls them deeper into the system.

Diverting young people away from court charges before that record forms has real long-term value. They keep their slate clean and their life options open. The catch, again, is delivery: diversion only works if the referral to treatment or support actually leads somewhere. A leaflet and a warning are not enough.

What Still Needs Answering

The study's design — bringing in police, health workers, and service providers from the start — shows what good research looks like. But it also raises practical questions that are not yet fully answered.

Which part of diversion actually reduces reoffending: the decision not to prosecute, the quality of the referral, or what happens at the treatment service afterward? Do all communities benefit equally, or do the racial disparities in who gets stopped and searched mean some people never access these programs in the first place? And how sloppy can a police force be before diversion stops being real intervention and becomes just a caution with extra paperwork?

These questions are not impossible to answer. The data exists. Whether police forces and local crime commissioners will fund the work to answer them is another story.