COINCIDING WITH A SERIES OF RECENT ACADEMIC PAPERS suggesting that executions deter the rate of homicide (Brumm and Cloninger 1996; Cloninger and Marchesini 2001; Mocan and Gittings 2003; Zimmerman 2004), the issues of capital punishment's efficacy (i.e., whether the death penalty reduces the incentive to participate in violent crimes) and equity (i.e., its apparent overapplication to poor and minority offenders) have once again entered the foray of political and social discourse. (1) However, the most heated debates on capital punishment often concern the normative concepts of its morality and/or ethicality. In particular, the various methods by which death penalty states carry out their executions has been one of the most controversial issues associated with capital punishment. Indeed, the commonly perceived "brutality" of particular methods of execution (such as electrocution and gas chamber asphyxiation) by opponents (as well as some proponents) of the death penalty has recently led to lethal injection being imposed as the sole method of execution in the majority of death penalty states.
Using a panel of state-level data over the years 1978-2000, this article brings together the issues of capital punishment's efficacy and method by examining the extent to which the latter affects (e.g., deters) the per capita incidence of murder in a differential manner. To this end, several measures of the subjective probability of being executed by the various methods are developed taking into account the timing of individual executions as in Mocan and Gittings (2003). The empirical estimates suggest that the deterrent effect of capital punishment is driven primarily by executions conducted by electrocution. This finding is consistent with a central tenet of the economic theory of crime: All else equal, the greater the (expected) severity of punishment, the less likely a rational agent will participate in criminal acts (Becker 1968). In the present context, more "brutal" methods of execution (e.g., electrocution) correspond to punishments of greater perceived severity and will thus tend to exhibit the strongest deterrent effect. None of the other four methods of execution are found to have a statistically significant impact on the per capita incidence of murder.
The findings with respect to electrocutions are robust to a variety of model specifications and controls for unobserved heterogeneity. Specifically, they are robust to the manner in which the subjective probabilities of being executed are defined, whether or not a state has a death penalty law on the books, the removal of state and year fixed effects, controls for state-specific time trends, simultaneous control of all execution methods, and controls for other forms of publicly provided deterrence. In addition, it is shown that the negative and statistically significant impact of electrocutions is not driven by the occurrence of a "botched" electrocution during the relevant time period.
The remainder of the article proceeds as follows. Section II summarizes the methods of execution employed by the death penalty states over the sample period and changes in the method of executing criminals across these states over time. Section III discusses the data and empirical methodology. Section IV presents the estimation results, and Section V concludes.
The Methods of Execution and Their Application Across the Death Penalty States
STATES WITH DEATH PENALTY LAWS have executed individuals convicted of capital offenses by one or more of five methods of execution (electrocution, lethal injection, lethal gas, hanging, and/or firing squad) since the U.S. Supreme Court's moratorium on the death penalty was lifted in 1976. Currently, 38 states (as well as the U.S. federal government and U.S. military) authorize executions. (2) Individual states that employ more than one method of execution administer a particular form based upon such factors as the choice of the inmate, the date the execution is carried out, and/or the possibility of a given method being held unconstitutional by a death penalty state's judicial system. …