Recent empirical studies by economists have shown, without exception, that capital punishment deters crime. Using large data sets that combine information from all fifty states over many years, the studies show that, on average, an additional execution deters many murders. The studies have received much publicity, and death penalty advocates often cite them to show that capital punishment is sound policy.
Indeed, deterrence is the central basis that many policymakers and courts cite for capital punishment. For example, President Bush believes that capital punishment deters crime and that deterrence is the only valid reason for capital punishment. Likewise, the Supreme Court, when it held in its landmark 1976 decision that capital punishment was constitutional, cited deterrence as one of its main reasons. Moreover, the Court confirmed that the main factor that motivated most state legislatures to prescribe capital punishment was deterrence. Similarly, a central issue in debates on whether federal law should include capital punishment is deterrence. We can also reasonably assume that juries and trial judges, in deciding whether to impose or overturn death sentences, will incorporate common understandings about deterrence. Governors may be similarly influenced in making decisions about clemency.