Council on Criminal Justice releases Illinois analysis of "The Public Safety Impact of Shortening Lengthy Prison Terms"

I keep noting this post from earlier this year discussing the Council of Criminal Justice's impressive Task Force on Long Sentences.  That Task Force keeps producing all sorts of interesting documents about long sentences (see prior posts here and here), and this latest report is authored by Avinash Bhati and titled "The Public Safety Impact of Shortening Lengthy Prison Terms."  This press release about the report provides this background and some particulars:

Shortening Illinois prison sentences of 10 years or more by modest amounts would result in very few additional arrests, cutting the state prison population significantly without jeopardizing public safety, according to a new analysis for a Council on Criminal Justice (CCJ) task force.

Reducing lengthy prison terms by as much as 30% would result in “a virtually undetectable increase” (less than one tenth of one percent) in annual arrests statewide, according to the report for CCJ’s Task Force on Long Sentences, which was produced in partnership with the Illinois Sentencing Policy Advisory Council (SPAC). Most additional arrests would be for drug, property, and other nonviolent crimes.

More than 1,100 people were released from Illinois prisons during the three-year study period, after serving a decade or more; the group served an average of nearly 19 years. While any additional arrests are cause for concern, the research estimates that reducing prison time served by those in the study group by one, two, or three years would result in between 11 and 37 additional arrests; in 2020, there were 89,173 total index crime and drug arrests in Illinois. No individual in the study group was estimated to have more than one additional arrest....

The research was conducted by the data analytics firm Maxarth LLC, which analyzed detailed arrest history data for the 1,127 people released from Illinois prisons between June 2016 and June 2019. For those who had served 10 years or more, researchers then created “microsimulations” to estimate the number of arrests that were averted due to the individuals’ long prison stays. (Details on the calculations and analysis can be found in the report methodology.)

Reductions in the size of the prison population, the analysis found, would range from a 2.4% drop if prison terms were trimmed by 10% (or 1.9 years), to a 7.2% cut if sentences were shortened by 30% (or 5.7 years). Such reductions represent potential cost savings. A separate 2021 analysis by SPAC found that a 3,000-person reduction in the average daily prison population, along with a reduction in staffing, could represent nearly $148 million in annual state correctional appropriations. Saltmarsh said that while these reductions in and of themselves would not automatically produce cost savings for Illinois, they could lead legislators to make different choices about how to fund IDOC’s general operations.