According to recent estimates, crime costs the community $32 billion annually. Of this, $1960 million is directly attributable to drugs, and, if indirect costs were included, the proportion attributable to drugs would be higher.1 Clearly, interventions that target potential risk factors for crime, such as drugs and mental health problems, will have significant payoffs for individuals and the wider community. However, the relationship between drugs and crime is complex. Policy development in this regard needs to take into account the multifaceted nature of the problem.

In this issue of the Journal (page 408), Heffernan et al present the first Australian publication that seeks to clinically assess the level of substance-use disorders and psychological distress among police arrestees.2 This article makes a constructive contribution to the evidence base. The study highlights that the overwhelming majority of arrestees suffer from clinical substance-use disorders and psychological distress, and that they are a population who may be in need of treatment. Replication of these findings is important to furthering our understanding of the need for treatment among this group.

In Australia, evidence is emerging (building on overseas research) that criminal behaviours among arrestee and prison populations vary widely, from minor disorderly conduct through to homicide, with different factors contributing to these behaviours. Illegal drug use is just one of many risk factors, but there is no doubt that it is significant in the behaviour of a subset of offenders. Recent analyses of police detainees and the incarcerated adult male population estimate that this is the case for between 34% and 52% of offenders.3,4 This clearly suggests that effective treatment interventions could significantly reduce crime rates.

Criminological studies that track when people start, persist with and desist from drug use and offending demonstrate that most offenders become involved in minor crime before experimenting with and using illegal drugs.5,6 For example, the onset of crime preceded regular heroin use in 69% of one sample of offenders.5 Illegal drug use seems to compound a pre-existing problem, and so produces higher levels of offending.7 Thus, treating substance misuse among offenders, although an essential public health measure, might not necessarily result in significant reductions in the number of offenders. This is because crime and drug use may be caused more by factors external to the individual, such as early-childhood experiences and development, access to labour markets, access to local drug markets and their supply routes, the social and cultural environment, lifestyle choices, and other determinants that are not easily amenable to treatment.8

The links between drug use and crime and the policy implications that flow from this will be affected by the nature of the local drug market. The Australian Institute of Criminology’s Drug Use Monitoring in Australia project has conclusively shown that police detainees’ drug use patterns vary across the country. Higher rates of amphetamine use have been detected in Queensland, Western Australia and South Australian sites; while higher rates of heroin use have been detected in New South Wales sites.9 Furthermore, breakdowns by offence type indicate that users of amphetamines are arrested for a range of offences, not just violence, and similarly heroin users are arrested for a range of offences, not just property. The links between drugs and offending types appear more variable than is often thought.

Changing human behaviour is difficult. Some people take drugs because they like the effects, some because they are risk takers, and some to self-medicate for past and current painful situations and events; others take them because they are addicted and simply cannot stop. Not everybody who is defined as dependent will want or seek treatment. In this complex environment, public policy responses, such as drug courts and court diversion systems, need to be cognizant of what drives behaviours and develop appropriate responsive systems (of which levels of dependency will be only one factor).

Recent evaluations of the south-east Queensland and NSW drug courts10,11 have shown that, even with a 12-month, structured, supervised program, some people continue to be criminally active and use illegal drugs. Estimates from the early stages of the Queensland study suggest about a third of graduates reoffended within the follow-up period after graduating from the court. Similarly, police diversion schemes need careful targeting, as good longitudinal research shows that, after a “first” contact with the criminal justice system, many young offenders (upwards of 60%) do not come back into contact with the juvenile system again.12-15

Because of the intersection between illegal drug use and crime, the criminal justice systems in Australia have developed a range of policy innovations to divert offenders into treatment and other programs. These include early police diversion programs, court-based initiatives to divert offenders into treatment, and formal drug courts for serious offenders. There have also been attempts to provide treatment programs within prisons. However, opportunities for diversion could be strengthened in other areas.

The first area is at the “end” of the criminal justice system, by providing postrelease support programs for prisoners leaving custody. Given that some 58% of prisoners have been imprisoned previously and 22% of police detainees have been imprisoned in the past 12 months, interventions to break the cycle of reoffending would have a significant beneficial effect on both the individual and the wider community — drug treatment is clearly one of those interventions.

The second opportunity to improve diversion to treatment is in the gap between police diversion and the drug court: targeting people who are arrested and processed but whose offence is not sufficiently serious to meet the criteria for a formal drug court program. The study by Heffernan et al includes a significant number of these people, providing support for “arrest drug referral” schemes, as undertaken in the United Kingdom.16 However, there could be very large numbers of people suitable for such schemes. Policymakers first need to know how many of those people would avail themselves of treatment. In addition, treatment options must exist — at present, there is a range of effective treatments for heroin, but options for other illegal drugs are extremely limited.

Reducing crime requires a multipronged approach that goes beyond criminal justice and treatment responses, to include a whole-of-government approach. Building the evidence base with valuable contributions such as that by Heffernan et al is vital to ensuring our interventions are successful.