Learning from the Limitations of Deterrence Research

Public policy and scientific knowledge concerning deterrence have long been marching in different directions. Despite the proliferation of threestrikes, mandatory minimum, and concealed weapons laws and retention of capital punishment in 37 states, there is little credible evidence that changes in sanctions affect crime rates, and there is no credible evidence that capital punishment deters better than life sentences or that allowing citizens to carry concealed weapons deters at all. There is evidence that changes in enforcement and sanctions can affect some kinds of behavior— for example, tax compliance, speeding, illegal parking—and there are plausible grounds for believing that other deterrable behaviors can be identified. Doing so will require fine-grained studies that take account of offender characteristics and perceptions, offending situations, and whether and how new enforcement strategies and sanctions systems are implemented. The state of the art of policy-relevant knowledge about the deterrent effects of the criminal justice system is little different in 2008 than it was 30 years ago when the National Academy of Sciences (NAS) panel on deterrence and incapacitation reported that the existence of a criminal justice system has overall deterrent effects, there is a widely shared intuition that penalty increases have marginal deterrent effects but the available evidence is highly ambiguous and contested, and there is no credible evidence that capital punishment deters homicide any more Michael Tonry is Sonosky Professor of Law and Public Policy and director, Institute on Crime and Public Policy, University of Minnesota, and senior fellow, Netherlands Institute for the Study of Crime and Law Enforcement, Leiden. He is grateful to Anthony N. Doob, Daniel Nagin, and Alex Piquero for reading and commenting helpfully on earlier drafts. This content downloaded on Thu, 3 Jan 2013 22:58:47 PM All use subject to JSTOR Terms and Conditions