Having a criminal justice system that imposes sanctions no doubt does deter criminal conduct. But available social science research suggests that manipulating criminal law rules within that system to achieve heightened deterrence effects generally will be ineffective. Potential offenders often do not know of the legal rules. Even if they do, they frequently are unable to bring this knowledge to bear in guiding their conduct, due to a variety of situational, social, or chemical factors. Even if they can, a rational analysis commonly puts the perceived benefits of crime greater than its perceived costs, due to a variety of criminal justice realties such as low punishment rates. These conclusions are reinforced by studies of crime rates following rule changes. Many show no change in deterrent effect. Those that purport to show a deterrent effect commonly have persuasive non-deterrence explanations, such as a change in incapacitative effect. The few studies that segregate deterrent and incapacitative effects tend to reinforce the conclusion that rule formulation has a deterrent effect only in those unusual situations in which the preconditions to deterrence exist. Even there, the deterrent effects are quite minor and unpredictable, hence inadequate grounds to influence criminal law rule making. Available for download at http://ssrn.com/abstract=660742
Robinson, Paul H., "Does Criminal Law Deter? A Behavioral Science Investigation" (2004). Faculty Scholarship at Penn Law. 31.