A systematic review found five studies that met the inclusion criteria established by their authors. Three of those five studies recorded positive effects of a small to medium magnitude, meaning that offenders who went through the courts were less likely to drink and drive again (usually during a two-year follow-up period), compared to those who were included in the control group. The other two studies revealed no significant differences between the two groups. However, the reviewers argued that the lack of statistically significant results in the latter two studies may be due to design flaws, such as too small of a sample or contamination between the treatment and control groups [1].
Three of the four experimental evaluations included in a second systematic review found considerable reductions in recidivism; however, one experimental evaluation (with a design that was more rigorous methodologically) found a negative effect. Thus, the authors conclude that, although there are indications of the efficacy of these courts, the evidence is inconclusive, and further studies with methodologically rigorous designs are still needed [2].