In a 2003 report, New York's Center for Court Innovation compared recidivism rates between drug court graduates and attendees from six different drug courts, and control groups of similar defendants not entering drug court. They found: "All six drug courts (Bronx, Brooklyn, Queens, Suffolk, Syracuse, and Rochester) produced recidivism reductions compared with conventional case processing. The six courts represent a mix of geographic areas and policies (e.g., regarding eligibility criteria, screening and assessment protocols, graduation requirements, approach to sanctions, and supplemental services). Since the measurement periods tracked defendants at least three years after the initial arrest and at least one year after program completion, the results indicate that positive drug court impacts are durable over time.
"The six drug courts generated an average 29% recidivism reduction over the three-year postarrest period and an average 32% reduction over the one-year post-program period."

Source

Rempel, Michael, Dana Fox-Kralstein, Amanda Cissner, Robyn Cohen, Melissa Labriola, Donald Farole, Ann Bader and Michael Magnani, "The New York State Adult Drug Court Evaluation: Policies, Participants and Impacts" (New York, NY: Center for Court Innovation, Oct. 2003), p. x.
http://www.courtinnovation.or…