By Roger Pryzybylski, John Maki, Stephanie Kennedy, AaronRosenthal and Ernesto Lopez

  Long prison sentences—defined here as sentences of 10 years or more—may be imposed for several reasons, including to punish people engaged in criminal behavior, to prevent individuals from committing additional crimes in the future, and to warn the general public about the consequences of violating the law. This literature review explores empirical evidence on the relationship between sentence length and public safety. It synthesizes the best available research on the incapacitation and deterrent effects of prison sentences and examines whether, and to what extent, prison sentences affect individual criminal behavior and overall crime rates. The relationship between long prison sentences and public safety is complex. Although long prison sentences may be warranted in individual cases based on one or more of the varied purposes of sentencing, the imposition of such sentences on a large scale offers diminishing returns for public safety. Research consistently shows that a relatively small percentage of individuals are responsible for an outsized share of crime in their communities. But attempts to use long sentences to selectively incapacitate this population have been unable to overcome competing factors like the “replacement effect,” where the incarceration of one person leads to another individual taking their place, and the “age-crime curve,” the criminological fact that offending typically decreases with age. Since relatively few studies have focused specifically on long prison sentences, this analysis encompasses the broader literature on incarceration and crime. The report concludes with recommendations for future research.  

Washington, DC: Council on Criminal Justice, 2022. 17p.