NCPA - National Center for Policy Analysis


June 15, 2005

Recent evidence suggests that capital punishment may have a significant deterrent effect, preventing as many as 18 murders for each execution, say Cass Sunstein and Adrian Vermeule of the AEI-Brookings Joint Center for Regulatory Studies.

Capital punishment presents a life-life tradeoff where a refusal to impose capital punishment could result in a significant increase in the number of deaths of innocent people. In other words, unjustified killing is exactly what capital punishment prevents, say the authors.

Recent research has strengthened the claim of Sunstein and Vermeule.

  • A study based on state-level data from 1977 to 1997 finds that each execution deters five murders on average.
  • Another study based on state-level data, this time from 1997-1999, found that a death sentence deters 4.5 murders and an execution deters three murders.
  • Additionally, the deterrent effect of the death penalty has been found to be a function of the length of waits on death row, with a murder deterred for every 2.75 years deducted from the period before execution.

Even the Supreme Court supports the idea, say Sunstein and Vermeule:

  • Using state-level date from 1960-2000, the Supreme Court made comparisons of the before-and-after effects of suspending and reinstating the death penalty; a substantial deterrent effect was found.
  • After suspending the death penalty, 91 percent of states faced an increase in homicides -- and in 67 percent of states, the rate was decreased after reinstatement of capital punishment.

Furthermore, the familiar problems with capital punishment -- potential error, irreversibility, arbitrariness and racial skew -- do not argue in favor of abolition, because the world of homicide suffers from those same problems in an even more acute form, say the authors.

Capital punishment may be morally required not for retributive reasons, but in order to prevent the taking of innocent lives, conclude Sunstein and Vermeule.

Source: Cass R. Sunstein and Adrian Vermeule, "Is Capital Punishment Morally Required? The Relevance of Life-Life Tradeoffs," AEI-Brookings Joint Center for Regulatory Studies, March 2005.


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