C. Evidence for therapeutic services and diversion from prosecution (Enforcement model)
There is highly processed and review-level evidence of the effectiveness of therapeutic services within criminal justice settings in reducing drug use and drug- related crime. As defined in the introduction to this document, Scottish policy directives are also supportive of this approach.
NICE Clinical Guideline 51 general considerations on drug misuse psychosocial interventions include :
The Advisory Council on Misuse of Drugs’ overview of the evidence on recovery from drug and alcohol dependence cites UK research evidence (Skodbo et al 2007) that coercion can be an effective way of getting people into treatment. 
A Scottish review of criminal justice interventions for drug users also concludes that equitable outcomes are achieved for those who access treatment through the criminal justice system as those who access it voluntarily. (Also citing previous work by Hough (1996) which concluded legally coerced treatment was no less effective than treatment entered into voluntarily and evidenced over time by McSweeney et al. (2006).) 
In their review of the evidence for supply control, Strang et al. (2012) surmise that although contested the evidence of effectiveness of sanctions such as wide-scale arrests and imprisonment as a deterrent of drug use and related criminal offending is at best weak. However, increasing evidence is cited from criminal justice programmes suggesting ‘specific, brief and immediate sentences (e.g. overnight)’ for individuals who fail drug tests in their supervision orders can produce considerable reduction in drug use and offending. The authors note this evidence comes from mandated abstinence programmes for drug and drink-driving offenders on community release, and programmes for addicted physicians and pilots.
There is review-level evidence that drug courts, as an intervention to support offenders into treatment, are more effective at retaining drug users than other diversion programmes, although the scale-up of such interventions is noted to have been challenging. 
Evidence of adult drug courts suggests that participants have reduced recidivism during and after drug court treatment, with effects lasting at least three years. Effectiveness is largely robust to programme variations. However, evidence supporting the importance of leverage and intensity (dismissing charges and more frequent status hearings) were significant in relation to specifically reducing drug-related recidivism. 
There is limited evidence from US-based models of family treatment drug courts that these can be effective in supporting parents to enter treatment, stay in longer and complete treatment. Some aspects were less conclusive, such as child welfare results. The basic model includes regular, frequent court hearings, intensive judicial monitoring, timely substance abuse treatment and other needed services, frequent drug testing, and rewards and sanctions linked to parental compliance with their service plan when the primary motivation for parents involved in FTDCs is the goal of being reunited with their children. Findings from a large-scale prospective study (Worcel et al., 2008) indicate that FTDCs did not decrease children’s stays in out of home placement, but they did increase the likelihood of the family being reunited. Clarity is needed as to whether this positive outcome is a result of the model’s influence on treatment or whether the model uniquely contributes to family reunification. 
There is evidence of effectiveness from multiple seminal large-scale longitudinal treatment outcome studies that treatment for drug dependence works to reduce drug use, improve mental and physical health, and reduce levels of crime [for a summary of findings see Best et al. (2010)]. Findings from these multiple ‘what works in practice’ studies at two to five years follow-up suggest a minimum three months treatment duration is critical to contributing to successful outcomes.
The Drug Treatment Outcomes Research Study (DTORS) is a major national longitudinal evaluation of drug treatment in England. Participants were recruited from treatment facilities between February 2006 and March 2007. Findings suggest evidence of treatment effectiveness with significant and substantial reduction in drug use and offending, with the criminal justice system (CJS) an equally valid route into drug treatment, with few differences in outcomes compared to non-CJS referrals. In addition, when the net gains in health from drug treatment and the savings in crime-related costs as a result of reduced offending were calculated, treatment was cost-effective and cost-beneficial.