Second Chances Resource Library

The analysis presented here was commissioned by the Task Force to examine the relationship between long prison sentences and public safety in one state, Illinois. The project was made possible by a partnership between the Illinois Sentencing Policy Advisory Council, CCJ, and Maxarth LLC, a data analytics firm. To examine this question, Maxarth LLC analyzed detailed arrest history data for people who were released from Illinois prisons between June 2016 and June 2019. For the 1,127 people in this release cohort who had served 10 years of more prior to release, microsimulations were created to estimate the number of arrests averted due to the individuals’ long prison terms.1 The number of arrests averted includes: (a) estimated arrests that did not happen because the person was incarcerated (incapacitation effect), (b) arrests that did not happen during a 30-month post-release tracking period because the person reduced their criminal activity (specific deterrence or rehabilitation effects), and (c) arrests that happened postrelease because the person increased their criminal behavior following their incarceration (criminogenic effect). The incapacitation effect was calculated using the length of each person’s prison stay (time served); the specific deterrence and criminogenic effects were calculated in the 30 months following each person’s release date.