seamus@psivax.UUCP (08/25/86)
In response to : >Can you reference any study which establishes that the death >penaly(sic) deters crime (primarily murder)? This is an often stated >defence of capitol punishment which is seldom backup (sic) with >evidence. > >david >_______ I am aware of three studies worthy of mention. One by a criminologist, Sellin, and two by economists, Ehrlich and Wolpin (references at end). The Economist Werner Hirsch (whom I highly respect) provides an excellent commentary on these studies in his text, "Law and Economics, An Introductory Analysis". NOTE- The following summary is mine and should not be blamed on anyone else. The studies attempt to determine if capitol punishment acts as a deterrent to the crime of murder. The study by Sellin indicated no correlation between capitol punishment and homicides while the studies by Ehrlich and Wolpin both indicated a deterrent effect. Sellin based his findings upon an analysis of clusters of neighboring states "closely similar" to each other. However, he failed to identify specific variables that influence the homicide rate and thus he could not show that the "closely similar" states were actually closely similar with respect to these variables. Hirsch comments, "...his clustering technique is a very weak attempt to hold other influences constant while examining differences in homicide rates." Ehrlich, using a simultaneous equation model, investigated the influence of three law enforcement variables on the number of homicides (probability of arrest per homicide, probability of conviction per arrest, and the probability of execution per homicide). He pointed out that "on the average the trade-off between the execution of an offender and the lives of potential victims it might have saved was of the order of magnitude of 1 for 8 for the period 1933-67 in the United States." Wolpin's study, utilizing English data, arrived at a ratio of 1 : 4 for executions to lives saved. -seamus references: 1. T. Sellin, "The Death Penalty", Philadelphia: American Law Institute, 1959 2. I. Ehrlich, "The Deterrent Effect of Capital Punishment: A Question of Life or Death", American Economic Review 65 June 1975 3. K. L. Wolpin, "Capital Punishment and Homicide in England", American Economic Review 68 May 1978 -------