This paper focuses on imprisonment, as it is the most severe, iconic and resource-intensive form of incapacitation. It is the form most commonly assumed to be effective and is the focus of most empirical research into this subject. The incapacitative effect of imprisonment presents a compelling logic: while in prison, an offender cannot offend in the community. Consequently, the incapacitation of an offender may be expected to prevent crime that an offender would commit were he or she at liberty in the community.