Prisons are good for punishing criminals and keeping them off the street, but prison sentences (particularly long sentences) are unlikely to deter future crime. Prisons actually may have the opposite effect: Inmates learn more effective crime strategies from each other, and time spent in prison may desensitize many to the threat of future imprisonment. See “Understanding the Relationship Between Sentencing and Deterrence” for additional discussion on prison as an ineffective deterrent.

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5. There is no proof that the death penalty deters criminals. According to the National Academy of Sciences, “Research on the deterrent effect of capital punishment is uninformative about whether capital punishment increases, decreases, or has no effect on homicide rates.”