Arguments in favor of incarceration, and other forms of harsh punishment, are typically rooted in one of four theories:

• Retribution - A person did something bad, so something bad should happen to them.

• Deterrence - Harsh punishments discourage people from breaking the law.

• Incapacitation - When someone is incarcerated, they can’t cause any harm. 

• Rehabilitation - Putting someone in prison after they commit a crime helps that person change in ways that will prevent them from committing crimes in the future. 

These theories inform the work of criminologists, are invoked in legislative debates about criminal legal policies, and come up in dinner table conversations about crime. Decades ago, discussion about these theories was largely theoretical, as there was little evidence of how well these theories worked in practice. That’s no longer the case. Scholars have amassed a large body of evidence about the impact of incarceration on crime generally and the efficacy of deterrence and incapacitation¹ specifically.

Incarceration is one of the most expensive and least effective ways to reduce crime, if it does so at all. Between 2009-2019, 37 states reduced both their crime and incarceration rates simultaneously, with those states reducing crime by 28% compared to only 18% in states that did not reduce their incarceration rate.² The reasons for this become clear once you dig down into the evidence on why and how crime and incarceration are linked. Multiple studies have proven that prison sentences do not deter crime, and other research has undermined key elements of incapacitation theory. The sections below take a deeper look at the evidence on two theories of deterrence (specific and general) and incapacitation.

Specific deterrence

What is the theory?

When an individual breaks the law, punishing that person harshly now will stop them from committing more crimes in the future. 

What does the evidence say? 

The short version: Sending people to prison or jail does not reduce the chances they’ll break the law in the future. 

The long version: A recent meta-analysis looks at 116 studies that compare people who were sentenced to jail or prison with people who received non-carceral sentences (i.e. probation). The study authors say: "Compared with noncustodial sanctions, custodial sanctions have a null to slightly criminogenic effect on reoffending." In other words, putting people in prison or jail either has no impact on their likelihood to commit a crime in the future (this is what “null effect” means) or makes them more likely to commit a crime after they get out (this is what “criminogenic effect” means). The authors go a step further than most academic authors are ever willing to go and say there is such a mountain of evidence behind the conclusion that prison sentences do not reduce future crime that it should be considered settled fact in the field. 

General deterrence

What is the theory?

The possibility of being punished harshly will discourage people from committing crimes. 

What does the evidence say? 

The short version: There’s very little evidence that general deterrence works, likely because most people don’t expect to be caught if they break the law and don’t know what the punishment will be if they are caught.

The long version: There are theoretical problems with general deterrence. First, the theory relies on people knowing the available punishment (how many people are thoroughly familiar with their state criminal code?). Second, the theory assumes that people will get caught, and more importantly, believe that they will get caught. General deterrence, like a lot of things in the social sciences, is tough to study, because states and countries and sentencing schemes are different, and it’s hard to compare them. But there’s little evidence that general deterrence is effective. That’s particularly true where crime, and specifically serious crimes like murder, are concerned. The effect of deterrence on administrative violations (like speeding) appears to be stronger than it is in the context of crime, possibly because speed limits are clearly posted and well understood. People generally don’t have detailed knowledge of criminal penalties, and they don’t expect to be caught when they commit a crime (and usually aren’t). 

Incapacitation

What is the theory?

As long as someone is incarcerated, they can't commit more crimes. 

What does the evidence say?  

The short version: Although keeping people in prison may prevent some crimes, research shows that the “marginal value,” that is the number of crimes prevented per person incarcerated, has decreased as the United States’ incarceration rate has exploded. Ultimately, incarceration may just shift crime inside of prison or to a later date, instead of preventing it.

The long version: A significant body of evidence demonstrates the weakness of incapacitation as a strategy for a variety of reasons.

First, because the United States already incarcerates such a tremendously large number of people, researchers have found there is very little “marginal benefit” to incarcerating more and more people.

Second, young people are far more likely than older people to commit crimes. (This is called the “age crime curve” in criminology.) Thus, imprisoning people into old age doesn’t prevent much, if any, crime at all.

Third, individuals convicted of serious, violent crimes, the ones we as a society would most like to prevent through incapacitation, are the least likely to commit more crimes after release from prison. One recent study found that the “‘incapacitation’ [...] effect is smaller than we typically assume. Preventing one person who was previously convicted of a violent crime from committing a new violent crime within five years of their sentence requires imprisoning 16 such individuals.” At the same time, nonviolent crimes, such as drug offenses, may not be prevented by incapacitation because of what is known as the “replacement effect.” Imprisoning someone who sells drugs on a street corner is not likely to end drug sales on that corner; someone else will simply take that individual’s place, resulting in no net change in crime (and even in more people being drawn into the criminal marketplace).

Fourth, most incapacitation studies don’t take into account one of the major findings from the recent meta-analysis on specific deterrence: prison makes people more likely to commit crimes in the future. So even if you were preventing crime in the short-term through incapacitation, you might just be delaying it until after the sentence is served.

Finally, crimes are also committed in prison, so incarcerating people doesn't necessarily reduce the total volume of bad things happening to people — in fact it creates new violence and harm for the people trapped inside and their families and communities.

Works Cited

1. Damon M. Petrich, Travis C. Pratt, Cheryl Lero Jonson, and Francis T. Cullen, “Custodial Sanctions and Reoffending: A Meta-Analytic Review,” Crime and Justice, September 2021, https://www.journals.uchicago.edu/doi/abs/10.1086/715100?journalCode=cj 

2. Dieter Dölling, Horst Entorf, Dieter Hermann and Thomas Rupp, “Is Deterrence Effective? Results of a Meta-Analysis of Punishment,” European Journal on Criminal Policy and Research, March 2009, http://blog.pucp.edu.pe/blog/wp-content/uploads/sites/470/2011/04/38029620.pdf 

3. Robert MacCoun, Rosalie Pacula, Jamie Chriqui, Katherine Harris, and Peter Reuter, “Do Citizens Know Whether Their State Has Decriminalized Marijuana? Assessing the Perceptual Component of Deterrence Theory,” Review of Law & Economics, January 2009, https://www.researchgate.net/publication/46556393_Do_Citizens_Know_Whether
   _Their_State_Has_Decriminalized_Marijuana_Assessing_the_Perceptual_Component_of_Deterrence_Theory 

4. Kirk R. Williams, Jack P. Gibbs, and Maynard L. Erickson, “Public Knowledge of Statutory Penalties: The Extent and Basis of Accurate Perception,” The Pacific Sociological Review, January 1980, https://www.jstor.org/stable/1388805 

5. Gary Kleck, “Deterrence: Actual Versus Perceived Risk of Punishment,” Encyclopedia of Criminology and Criminal Justice, November 2018, https://link.springer.com/referenceworkentry/10.1007/978-1-4614-5690-2_408 

6. Shima Baradaran Baughman, “How Effective Are Police? The Problem of Clearance Rates and Criminal Accountability,” University of Utah College of Law Research Paper No. 362, April 2020, https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3566383 

7. Rucker Johnson and Steven Raphael, “How Much Crime Reduction Does the Marginal Prisoner Buy,” The Journal of Law and Economics, May 2012, https://gsppi.berkeley.edu/~ruckerj/johnson_raphael_crimeincarc_JLE.pdf

8. Lauren-Brooke Eisen, Oliver Roeder, and Julia Bowling, “What Caused the Crime Decline,” Brennan Center for Justice, February 2015, https://www.brennancenter.org/our-work/research-reports/what-caused-crime-decline 

9. Michael Rocque, Chad Posick, and Justin Hoyle, “Age and Crime,” The Encyclopedia of Crime and Punishment, October 2015, https://doi.org/10.1002/9781118519639.wbecpx275 

10. Matthew R. Durose and Leonardo Antenangeli, “Recidivism of Prisoners Released in 34 States in 2012: A 5-Year Follow-Up Period (2012-2017),” Bureau of Justice Statistics, July 2021, https://bjs.ojp.gov/sites/g/files/xyckuh236/files/media/document/rpr34s125yfup1217.pdf

11. David J. Harding, “Do Prisons Make Us Safer,” Scientific American, June 2019, https://www.scientificamerican.com/article/do-prisons-make-us-safer/

12. Mark A.R. Kleiman, “Toward (More Nearly) Optimal Sentencing for Drug Offenders,” Criminology and Public Policy, March 2006, https://drive.google.com/file/d/0B6taQDF0rdAwYnJNTDU2bDVBNFU/edit?resourcekey=0-cKmokRCTqy3ItCVi74EbwQ

13. Christopher Torres, Stewart J D'alessio, and Lisa Stolzenberg, “The Replacements: The Effect of Incarcerating Drug Offenders on First-Time Drug Sales Offending,” Crime & Delinquency, October 2020, https://www.researchgate.net/profile/Christopher-Torres/publication/345032654_The_Replacements_The_Effect_of_Incarcerating_Drug_Offenders_on_First-Time_Drug_Sales_Offending/links/5f9c6ea9458515b7cfac84d7/The-Replacements-The-Effect-of-Incarcerating-Drug-Offenders-on-First-Time-Drug-Sales-Offending.pdf

14. Josh Voorhees, “A City of Convicts,” Slate, June 2014, https://slate.com/news-and-politics/2014/06/prison-crime-rate-the-u-s-violent-crime-rate-is-falling-partly-because-the-justice-department-ignores-the-countless-crimes-that-take-place-in-prisons.html#lf_comment=182959277

15. Emily Widra, “No escape: The trauma of witnessing violence in prison,” Prison Policy Initiative, December 2020, https://www.prisonpolicy.org/blog/2020/12/02/witnessing-prison-violence/

16. FWD.us, “Every Second: The Impact of the Incarceration Crisis on America’s Families,” December 2018, https://everysecond.fwd.us/

17. Eric Reinhart and Daniel L. Chen, “Association of Jail Decarceration and Anticontagion Policies With COVID-19 Case Growth Rates in US Counties,” JAMA Network Open, September 2021, https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2783680?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=090221

This report was produced in collaboration with FWD.us. 

Contributors: Laura Bennett, Director of The Center for Just Journalism, and Felicity Rose, Director of Research and Policy at FWD.us