"In the evaluations we reviewed, adult drug-court program participation was generally associated with lower recidivism. Our analysis of evaluations reporting recidivism data for 32 programs showed that drug court program participants were generally less likely to be re-arrested than comparison group members drawn from the criminal court system, although the differences in likelihood were reported to be statistically significant in 18 programs.38 Across studies showing re-arrest differences, the percentages of drug court program participants rearrested were lower than for comparison group members by 6 to 26 percentage points. One program did not show a lower re-arrest rate for all drug-court program participants relative to the comparison group within 3 years of entry into the program, although that study did show a lower re-arrest rate for drug court participants who had completed the program than for members of the comparison group. In general, the evaluations we reviewed found larger differences in re-arrest rates between drug-court program completers and members of the comparison group than between all drug-court program participants and the comparison group members. The rearrest rates for program completers ranged from 12 to 58 percentage points below those of the comparison group.39 The completion rates reported in the evaluations we reviewed ranged from 15 percent to 89 percent."

Source

"Adult Drug Courts: Studies Show Courts Reduce Recidivism, but DOJ Could Enhance Future Performance Measure Revision Efforts" (Washington, DC: Government Accountability Office, Dec. 2011), GAO-12-53, pp. 19-20.
http://www.gao.gov/assets/590…