Proponents of the death penalty say it deters people from committing crimes, especially violent crimes like murder. In other words, when execution is a potential consequence, rates of violent crime decrease. Opponents of the death penalty, however, argue that executions “brutalize” society by officially diminishing the respect for life. This in turn increases the rate of violent crimes. In this blog post, I want to explore the data surrounding this debate, and try to determine whether or not the death penalty is a deterrent for crime.
Let’s begin by looking at the context surrounding the issue. Currently, the U.S. is one of 57 countries worldwide which retain the practice of capital punishment—a.k.a the death penalty.
However, in the U.S., only 31 states, the federal government, and military still use capital punishment as a legal penalty.
According to a 2013 Pew Research survey, 55 percent of American adults surveyed said they favored the death penalty for persons convicted of murder. Compared to only 37 percent who said they opposed the practice.
Across demographic groups, the percentage of those in favor of the death penalty is also higher than those opposed.
Despite extensive research on this topic criminologist, statisticians, and politicians have been unable to prove the death penalty has any effect on crime rates. ([Washington Post] [Dartmouth College] [University of Pennsylvania]) In 2012, the National Research Council released a report reviewing three decades of research. The committee in charge of the report stated:
“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.”
In the report, the National Research Council outlined three “fundamental flaws” of the existing studies on deterrence:
- The studies do not factor in the effects of non-capital 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.
Other common problems when reviewing deference studies include: correlation vs. causation, confounding variables (uncontrolled experiments), declining overall rates of executions, and the differences between deterring petty crime and violent crime. As the department of criminology at the University of Pennsylvania says, “One cannot study the impact of executions when they are hardly ever imposed, and it is difficult to separate any impact of the death penalty from the large number of other factors that affect the amount and kinds of crime.” At the end of the day, neither side of the debate can claim to have empirical support.
If this were a digipo article, the short answer to my question would be: can’t tell. Essentially, research cannot tell if the death penalty influences crime at all, let alone if it deters violent crime. This answer was equal parts expected and surprising. Growing up, I was told there was no evidence that the death penalty was an effect deterrent. However, I had no idea how inconclusive the whole field of research was. Yet, despite ambiguous research, I think the death penalty is falling out of favor. Even in states where capital punishment is legal, the rate of executions has been steadily decreasing over the last decade. I think it’s likely the U.S. will abolish capital punishment before any conclusion is reached from the data.