The effects of custodial vs. non-custodial sentences on re-offending: A systematic review of the state of knowledge

As part of a broad initiative of systematic reviews of experimental or quasiexperimental evaluations of interventions in the field of crime prevention and the treatment of offenders, our work consisted in searching through all available databases for evidence concerning the effects of custodial and non-custodial sanctions on reoffending. For this purpose, we examined more than 3,000 abstracts, and finally 23 studies that met the minimal conditions of the Campbell Review, with only 5 studies based on a controlled or a natural experimental design. These studies allowed, all in all, 27 comparisons. Relatively few studies compare recidivism rates for offenders sentenced to jail or prison with those of offenders given some alternative to incarceration (typically probation). According to the findings, the rate of re-offending after a non-custodial sanction is lower than after a custodial sanction in 11 out of 13 significant comparisons. However, in 14 out of 27 comparisons, no significant difference on re-offending between both sanctions is noted. Two out of 27 comparisons are in favour of custodial sanctions. Finally, experimental evaluations and natural experiments yield results that are less favourable to non-custodial sanctions, than are quasi-experimental studies using softer designs. This is confirmed by the meta-analysis including four controlled and one natural experiment. According to the results, non-custodial sanctions are not beneficial in terms of lower rates of re-offending beyond random effects. Contradictory results reported in the literature are likely due to insufficient control of pre-intervention differences between prisoners and those serving “alternative” sanctions