The death penalty and deterrence are frequently linked concepts with a controversial connection. In the 20th century, one of the primary arguments for the use of the death penalty focused around the concept that fear of execution will deter crime. Although there is not a consensus on the issue, many experts suggest that the majority of studies done on the death penalty and deterrence do not actually show any connection that indicate a reduction of crime caused by fear of execution.
It is difficult to pinpoint the moment in history when the death penalty and deterrence became inextricably linked. Fear of the law resulting in good behavior seems to have long been a part of legal structures, particularly in eras and regions where torture was allowed on top of simple executions. The first real arguments against the death penalty, made during the Enlightenment period in Europe, centered around the concept that revenge killing is inhumane and detrimental to societal progress. At some point in history, with wrangling over the moral question of state-sanctioned murder largely unsolved, the debate shifted to the importance of execution as a means of maintaining order through deterrence. From that pivotal shift onward, efforts have been focused on measuring, to any extent, the effect the death penalty, or lack thereof, has on crimes.
The criteria for measuring the link between the death penalty and deterrence is almost always a source of controversy in itself. Some experts claim that, when considering criminal activity and the death penalty, it is only fair to measure crimes that could reasonably bring about the death penalty in consequence. For instance, since stealing a toothbrush would never incur the death penalty, toothbrush-stealing could not truly be said to be deterred by the existence of the death penalty. This restriction tends to limit the scope of crime examined to instances of brutal murders that might qualify for capital punishment. Agreeing to that limitation, however, is not always a given.
One of the largest problems with nearly all the studies done on the death penalty and deterrence is that few can agree on the correct methodology, and many dispute conclusion drawn from data. This means that while the majority of studies do not show a link, these studies are far from universally accepted as objective or scientifically sound. Studies that do show a connection between the death penalty and deterrence are subject to the same criticisms, leaving many to determine a personal view of the deterrence effect based on a personal view of correct scientific procedures.
The primary rational arguments on both sides are distinguished by a few key principles. Those who do not believe in a link often cite the fact that people that commit crimes worthy of execution consideration are not thinking about the consequences; often, these crimes are gang-related, which means that the perpetrators frequently exist in a situation where torture and murder is an everyday consideration, therefore being executed by the state might actually be a more humane future. Those that do believe in a link tend to argue that not only do people inherently fear death, thus are likely to fear the death penalty, but execution unquestionably prevents the convicted criminal from committing anymore crimes, thus is a deterrent on an individual level.