The theory of incapacitation, as it relates to crime control, states that offenders who are housed in jails, prisons, or any other location that limits their movements and freedom will prevent these individuals from committing crimes. The theory continues that crime rates will decrease as the rate of incarceration increases. Collective incapacitation involves standardized guidelines for the sentencing of any offender for a specific offense (Visher, 1987). The logic behind collective incapacitation is that all offenders who commit the same type of crime or a crime of the same seriousness should serve equivalent sentences. Selective incapacitation, however, attempts to customize sentencing based on the individual offender (Visher, 1987). Under this model, the offenders most likely to commit more crime would serve longer sentences than those less likely to commit crime.
There are two primary methods of estimating the incapacitation effect. The first method involves studying the offenders themselves (DiIulio & Piehl, 1991). This method usually involves some form of self-report survey and uses figures provided by offenders. Using these methods is rather complex and brings several advantages and disadvantages that must be examined in context with the actual findings before a conclusion can be reached. First, self-report surveys have the advantage of being able to tap into the dark-figures of crime, crimes that are not reported to the police or that are not cleared by the police. Offenders are able to report on how many actual crimes they committed and not just on those for which they have been incarcerated.
Unfortunately, this advantage is also a complex disadvantage (DiIulio & Piehl, 1991). Researchers have no way of knowing if an offender is being truthful when reporting past offenses. Offenders may feel the need to underreport their offending for fear of repercussion or they may over-report their offending in an attempt to skew the research or as a way to make themselves look better. These possibilities must be taken into consideration when conducting this type of research. In addition, there is also a chance that one or two offenders will report levels of offending much higher or much lower than the other offenders in the study. When this happens these figures are known as outliers and can affect research results if not properly taken care of by the researcher.
A second method of estimating the incapacitation effect is by utilizing macro-level studies. A macro-level study involves collecting data from a large, geographical location (Spelman, 2000). When studying incapacitation, states are usually studied by comparing a states’ prison population with that states’ overall crime rates. Unfortunately, using this type of study, it is difficult to make conclusions about the incapacitation effect due to the inability of the researcher to account for other variables that could affect crime rates. There is also the problem of generalizability of the research from one state to the next.
It is difficult to classify the incapacitation theory as an overall success or failure. There is much mixed research on the topic. DiIulio and Piehl (1991) highlight the difficulties associated with finding an incapacitation effect using self-report surveys. The variation between number of crimes committed per year between offenders, the social costs saved per crime and the cost of incarceration per offender per year are all figures that vary between locations and must be taken into account before any benefit can be established. Spelman (2000), using a macro-level study, estimates the incapacitation effect between 0.16 and 0.31 percent per one percent prison population increase. For many, this small benefit is not worth the cost.
DiIulio, J. J., Jr. and A. M. Piehl. (1991). “Does Prison Pay?” The Brookings Review 9 (Fall):28-35.
Spelman, W. (2000). “What Recent Studies Do (and Don’t) Tell Us about Imprisonment and Crime.” Pp. 419-494 in M. Tonry (ed.), Crime and Justice: A Review of Research, Vol. 27. Chicago: University of Chicago Press.
Visher, C. A. (1987). “Incapacitation and Crime Control: Does a ‘Lock ‘Em Up’ Strateg Reduce Crime?” Justice Quarterly 4:413-543.