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Cutting Prison Term Lengths Would Yield Few New Crimes, Study Says

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


Reducing lengthy prison terms by as much as 30 percent would result in "a virtually undetectable increase” (under one tenth of one percent) in annual arrests statewide, says the report for CCJ’s Task Force on Long Sentences, produced 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 after serving a decade or more; the group served an average of nearly 19 years.

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 group was estimated to have more than one additional arrest.

“Understanding the relationship between long sentences and public safety is critical for policymakers, and this research advances that understanding substantially,” said the CCJ task force's John Maki. “It’s a powerful reminder of the diminishing returns of lengthy prison terms. Most people ‘age out’ of criminal behavior as

they near the end of a long sentence, and shortening their time behind bars can be done with minimal impact on community safety.”

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.

Reductions in the size of the prison population would range from a 2.4 percent drop if prison terms were trimmed by 10 percent (1.9 years), to a 7.2 percent cut if sentences were shortened by 30 percent ( 5.7 years).

An 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.

An earlier report from the task force said that long sentences prevent some crime from occurring through an incapacitation effect, although estimates of the magnitude of the crime-prevention effects are

inconsistent and vary by crime type.

The task force, headed by former U.S. Deputy Attorney General Sally Yates and former U.S. Rep. Trey Gowdy (R-SC), is examining how prison sentences of 10 years or more affect incarcerated people and their families, victims and survivors of crime; correctional staff; communities; and public safety.

The panel is expected to release recommendations for changes to policy and practice in March.

Support for the effort comes from Arnold Ventures, the Ford Foundation, Southern

Company Foundation, and Stand Together Trust, as well as #StartSmall, the John D. and

Catherine T. MacArthur Foundation, and other contributors.


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