Deterrence

The stream of research papers and the accompanying theoretical discussions have above all clarified the methodological problems and illustrated the limitations of different research methods. The research has produced fragments of knowledge that can be of use to check and supplement commonsense reasoning, which will have to be relied on for a long time to come. There is a long way to go before research can give quantitative forecasts about the effect on crime rates of contemplated changes in the system. Some researchers have tried to quantify their findings. The best-known example is Isaac Ehrlich's controversial work on the effects of capital punishment on the murder rate. According to Ehrlich, statistics on the use of capital punishment in the United States in the years from 1933 to 1969 indicated that each execution in this period had prevented seven to eight murders. The study has been severely criticized (see Beyleveld), and such quantitative assessments seem clearly premature.

It may be asked how far the problems of deterrence are at all researchable. The long-term moral effects of criminal law and law enforcement are especially hard to isolate and quantify. Some categories of crime are so intimately related to specific social situations that generalizations of a quantitative kind are impossible. One may think of race riots, corruption among politicians and public employees, and many types of white-collar crime. An inescapable fact is that research will always lag behind actual developments. When new forms of crime come into existence, as did hijacking of aircraft or terrorist acts against officers of the law, there cannot possibly be a body of research ready as a basis for the decisions that have to be taken. Common sense and trial and error have to give the answers.