About the author: This article was written by Ulrike Ruppin. Ulrike is a PhD student researching the well-being of patients with GID in a long-term follow-up study at the University of Ulm, and is currently working at the Clinic for Forensic Psychiatry and Psychotherapy in Günzburg.
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Remember to also read our articles "Should we be tough on crime?" and "Does deterrence reduce crime?".
Most countries have carried out the death penalty, also known as capital punishment, at some point in history. Today, more than two-thirds of all countries have abolished it; 130 countries have abolished its legal practice, and 9 countries use the death penalty only for exceptional crimes such as crimes of war . In contrast, 58 countries retain the death penalty for ordinary crimes, including Belarus as the only European country and the United States as the only country in the G8. In 2011, new death sentences were imposed for 1923 offenders in 63 countries, and 676 people were executed in 20 countries (not including China) . A primary reason given to justify the retention of capital punishment is the prevention or deterrence of recidivism. It may act as a specific deterrent by discouraging offenders from re-offending or as a general deterrent aiming to prevent crimes from being committed in general by making examples of specific offenders. In particular, according to deterrence theory, the threat of capital punishment should act to discourage the commission of capital offences (i.e., crimes punishable by death, such as homicide) more effectively than the prospect of long-term or life imprisonment .
One way of testing this assumption is to examine how the number of executions carried out relates to the number of homicides committed in a given year. Empirical studies on this topic are often conducted by economists with some claiming to have found an additional deterrent effect of the death penalty compared to long-term or life imprisonment. One study found that “each additional execution decreases homicides by about five, and each additional commutation [of a death sentence to a long prison term] increases homicides by the same amount” . From 1967 to 1976, there was a moratorium on executions in the United States. Researchers have used this freeze in practice to further quantify the deterring effect of capital punishment. In one study, higher rates of homicide were found in 91% of the states after suspension of the death penalty; the reinstatement of capital punishment legislations was followed by a decrease in homicide rates in 70% of states across the US .
Despite these findings, there still remains a lack of consensus among researchers on the effect of capital punishment as a crime deterrent, with the results of many studies challenging the above findings. One method of studying the deterring effect of death sentences is to compare homicide rates in states that have never had the death penalty to the other states in the US. Researchers examining this have concluded that “most of the action in homicide rates in the United States is unrelated to capital punishment.”  Further, an extensive survey given to leading criminologists asking for their expert opinions regarding whether the death penalty served as a more effective deterrent than long-term imprisonment showed a strong consensus: The experts agreed that the death penalty has no additional effect on deterring capital crimes .
When talking about capital punishment, it is not enough to consider empirical studies because they do not fully capture the complexity of this issue. The same is true for court decisions. According to the Innocence Project, an organization dedicated to exonerating wrongfully convicted people, between 2.3% and 5% of all incarcerated offenders in the United States are innocent . Additionally, the killing of a human being by the state violates several human rights as proclaimed in the Universal Declaration of Human Rights: the right to human dignity (article 1), the right to life (article 3), and the right to not to be subjected to cruel, inhuman or degrading punishment (article 5).
So, does the death penalty reduce crime? The answer is: we do not know. However, according to the literature, there are a substantial number of experts who do not support the effectiveness of the death penalty, or the assumptions underlying it. In sum, in addition to human, legal, and moral reasons, there are also scientific reasons to appreciate the global trend towards abolition of the death penalty.
“We have surveyed data on the time series of executions and homicides in the United States, compared the United States with Canada, compared non-death penalty states with executing states, analyzed the effects of the judicial experiments provided by the Furman and Gregg decisions comparing affected states with unaffected states, surveyed the state panel data since 1934, assessed a range of instrumental variables approaches, and analyzed two recent state-specific execution moratoria. None of these approaches suggested that the death penalty has large effects on the murder rate.”
– John Donohue and Justin Wolfers, experts on law and economics
"Our survey indicates that the vast majority of the world’s top criminologists believe that the empirical research has revealed the deterrence hypothesis for a myth.”
- Michael Radelet and Traci Lacock, experts on criminology.
"The evidence presented to me by former prosecutors and judges with decades of experience in the criminal justice system has convinced me that it is impossible to devise a system that is consistent, that is free of discrimination on the basis of race, geography or economic circumstance, and that always gets it right."
– Governor Pat Quinn of Illinois, USA, speaking about his decision to seek an end to the death penalty.
Overview of Controversies covered to date
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