We could cut sentences for violent crimes by half in most instances without significantly undermining deterrence or increasing the threat of repeat offending. Studies have found that longer sentences do not have appreciably greater deterrent effects; many serious crimes are committed by people under the influence of alcohol or drugs, who are not necessarily thinking of the consequences of their actions, and certainly are not affected by the difference between a 15-year and a 30-year sentence.

For the same conduct, we impose sentences on average twice as long as those the British impose, four times longer than the Dutch, and five to 10 times longer than the French. One of every nine people in prison in the United States is serving a life sentence. And some states have also radically restricted parole at the back end. As a result, many inmates are held long past the time they might pose any threat to public safety.

Offenders “age out” of crime — so the 25-year-old who commits an armed robbery generally poses much less risk to public safety by the age of 35 or 40. Yet nearly 250,000 inmates today are over 50. Every year we keep older offenders in prison produces diminishing returns for public safety. For years, states have been radically restricting parole; we need to make it more readily available. And by eliminating unnecessary parole conditions for low-risk offenders, we can conserve resources to provide appropriate community-based programming and supervision to higher-risk parolees.