A report released on April 18 by the pres­ti­gious National Research Council of the National Academies based on a review of more than three decades of research con­clud­ed that stud­ies claim­ing a deter­rent effect on mur­der rates from the death penal­ty are fun­da­men­tal­ly flawed. The report con­clud­ed: ​“The com­mit­tee con­cludes that research to date on the effect of cap­i­tal pun­ish­ment on homi­cide is not infor­ma­tive about whether cap­i­tal pun­ish­ment decreas­es, increas­es, or has no effect on homi­cide rates. Therefore, the com­mit­tee rec­om­mends that these stud­ies not be used to inform delib­er­a­tions requir­ing judg­ments about the effect of the death penal­ty on homi­cide. Consequently, claims that research demon­strates that cap­i­tal pun­ish­ment decreas­es or increas­es the homi­cide rate by a spec­i­fied amount or has no effect on the homi­cide rate should not influ­ence pol­i­cy judg­ments about cap­i­tal pun­ish­ment.” (empha­sis added). Criminologist Daniel Nagin of Carnegie Mellon, who chaired the pan­el of experts, said, ​“We rec­og­nize this con­clu­sion will be con­tro­ver­sial to some, but nobody is well served by unfound­ed claims about the death penal­ty. Nothing is known about how poten­tial mur­der­ers actu­al­ly per­ceive their risk of punishment.”

The report found three fun­da­men­tal flaws with exist­ing stud­ies on deterrence:

  • The stud­ies do not fac­tor in the effects of non­cap­i­tal pun­ish­ments that may also be imposed.
  • The stud­ies use incom­plete or implau­si­ble mod­els of poten­tial mur­der­ers’ per­cep­tions of and response to the use of capital punishment.
  • Estimates of the effect of cap­i­tal pun­ish­ment are based on sta­tis­ti­cal mod­els that make assump­tions that are not credible.

(D. Nagin and J. Pepper, ​“Deterrence and the Death Penalty,” Committee on Law and Justice at the National Research Council, April 2012; D. Vergano, ​“NRC: Death penal­ty effect research ​‘fun­da­men­tal­ly flawed’,” USA Today, April 18, 2012.) See Deterrence and Studies. Read the NRC’s Report Brief (4 pages).

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