I find no conclusive evidence to support the view that the death penalty is or is not an effective deterrent in controlling crime. Opponents of capital punishment argue that it is not a deterrent, because in some states where capital punishment is allowed the crime rate goes up. Others argue that capital punishment deters violent crime, though it is difficult to provide numerical evidence. Dozens of studies have examined the relationship between murder and the death penalty comparing murder rates in areas with the death penalty to those in areas without the death penalty.
Murder rates have been examined when the death penalty was added or removed in various areas and countries. None of these studies establish that the death penalty results in lower murder rates or that the abolition of the death penalty increases murder rates. If the death penalty deters, the deterrent effect is so small that even the most sophisticated attempts have been unable to measure it. Studies have suggested that the death penalty is no more effective than imprisonment in deterring others from committing violent crime.
General deterrence is the idea that punishing an offender deters others from committing similar crimes. Specific deterrence refers to the fact that executing a known offender prevents that person from killing again, deterring at least that specific offender. Certainly, capital punishment will not deter all crime. Evidence suggests that psychotic and deranged killers, members of organized crime, and street gangs do not appear to be deterred from committing acts of murder by the implementation of capital punishment.
A person who is irrational or wants to commit a murder will do so whether capital punishment exists or not. Homicides are an act of passion, an impulsive act committed under tremendous stress and/or the influence of alcohol or drugs by individuals prone to aggressive, impulsive behavior. These people do not make rational calculations of pain and gain at the time of their acts. There are, of course, some carefully planned, premeditated murders. However, people committing these murders usually do not expect to be caught. For deterrence to work, the potential offender must see the penalty as a significant threat.
But some people commit murder as a way of punishing themselves or of committing suicide. Others see it as a way to gain notoriety. For them, the consequence is an attraction, and may explain why executions encourage some homicides. Preventing the recurrence of murder is certainly a serious concern, and families of murder victims wrestle with this issue, as we all must. So the question still remains as to whether capital punishment actually deters more effectively than other forms of severe punishment, because there is very little evidence that supports a deterrent effect.