In 2011, the State of California released more than 27,500 inmates from state prison as the result of a court order. A recent study, published online by the journal Criminology and Public Policy, is among the first to evaluate the effect of these releases on crime rates (paywall). Professors from three American universities examined data from the state and found there was no change in crime rates as a result of the releases.
In 2009, a federal court ordered the State of California to reduce it’s prison population to 137.5% of it’s designed capacity. According to the court, overcrowding had risen to the level of cruel and unusual punishment. (The population had been 181% of capacity.) Two years later, in a landmark decision, the US Supreme Court upheld that order. To accomplish those reductions, the state passed the Public Safety Realignment Act, a law that mandated a variety of reforms, including releasing some non-violent offenders.
In order to rule out other factors that might have caused a change in crime rates, the researchers treated California as a sort of natural experiment. They used the other 49 states as a control group, so that they could verify that any change in crime rates was the result of the prison releases, rather than some unrelated cause.
Their results show no statistically significant variation in California’s crime rates in the three years after the releases, with the exception of a brief surge in auto thefts. They estimate that in the year after the releases there were somewhere between 18 and 130 additional auto thefts per 100,000 residents. By the following year that increase had subsided. The violent crime rate was unaffected throughout.
It is possible that other changes during the time period could have offset the effects of the prison releases, but that seems very unlikely. A study from the California Department of Corrections found little difference between the behavior of those released as part of the realignment (pdf), and those released previously. The new research provides strong support for the idea that at least some prisoners can be released from incarceration without creating any additional risk to public safety.