Does the death penalty deter crime?

Fifty one years ago the United Kingdom became the fourteenth country to officially abolish the death penalty. By 1977, 16 countries had abolished the death penalty in law or practice. Today, the number has risen to 140.

However, while the number of countries practising the death penalty has continued to decline, the number of people executed has increased in recent years. According to Amnesty International, more people were executed worldwide in 2015 than in any year since 1989. Three countries were responsible for almost 90% of the executions in 2015; Iran, Saudi Arabia and Pakistan.

One of the key justifications for the use of the death penalty is that it deters crime. For example, Hassan Rouhani, the President of Iran, who has presided over the execution of over 1,200 people since his election in 2014, has argued that abolishing the death penalty would lead to a rise in crime in the country. This article explores the evidence behind those claims.

Evidence from America

The United States has provided an excellent venue for researchers examining the question of whether the death penalty deters crime. The US provides such a good environment for two reasons. First, the use of the death penalty varies between individual states. This allows researchers to compare crime rates between states that retain capital punishment and states that do not. Second, in 1972, the US Supreme Court effectively abolished the death penalty for four years. This created an ideal natural experiment for which researchers could compare crime rates during the ‘moratorium’ and before or after it.

Comparing US states

A number of studies have shown that states with the death penalty generally experience higher homicide rates than states without it. For example, Amnesty International found that the murder rate in non-death penalty states has remained consistently lower than the rate in states with the death penalty. The New York Times have reported similar findings. They found that the 83% of US states without the death penalty had homicide rates below the national average.

The ‘moratorium’

A number of studies have purported to show that the US Supreme Court’s decision to effectively abolish capital punishment in 1972 led to an increase in homicide rates. For example, one study compared the homicide rate during the moratorium (1972 - 1976) with the homicide rate after the moratorium (1977 - 1997). The authors find a substantial deterrent effect. They conclude that the "data indicates that murder rates increased immediately after the moratorium was imposed and decreased directly after the moratorium was lifted, providing support for the deterrence hypothesis.”

Ostensibly, the increase in homicide rates during the moratorium and subsequent decrease after provide a compelling case for the the deterrent effect of capital punishment. However, more recently these studies have faced significant criticism. The aforementioned study only compared states that were affected by the Supreme Court’s decision. That is, they only examined states that had the death penalty in 1971 and had reinstated it by 1977. A later study also included states that were not affected by the Supreme Court’s decision because they had abolished the death penalty prior to 1972. Using these states as a control group, the authors were able to show that the moratorium did not cause a rise in homicide rates.

American exceptionalism?

While the evidence from the United States suggest that the death penalty does not have a detrimental effect on crime rates, it is possible these results may not be applicable to the rest of the world.

Comparing the crime rates of countries which retain the death penalty and countries which have abolished it is problematic. This is because the vast cultural differences between countries can obscure trends and relationships. Because of this, researchers have tended to examine crime rates in countries that have abolished the death penalty, before and after.

For example, one study examined the abolition of the death penalty in Canada. The study found that the homicide rate per 100,000 of the population fell from a peak of 3.09 in 1975, the year before the death penalty for murder was abolished, to 2.41 in 1980. The homicide rate in Canada has remained significantly lower than before abolition ever since. A further study examined the murder rates in Hong Kong for a 35-year period beginning in 1973 and found that the abolition of capital punishment had little impact on crime levels.


The number of countries abolishing the death penalty continues to rise but, at the same time, the number of people being executed has experienced a recent rise. This is an extremely worrying trend. One of the leading justifications for the use of the death penalty is that it deters crime. This claim has been repeatedly tested by researchers. The majority of research from both the US and worldwide has found no evidence of a deterrence effect.

James Dobson is a researcher for Bright Blue