Deterrence is a myth  The deterrent effect of prison is uniformly overstated. It is popularly thought that the indignity and strictness of the prison environment will discourage criminal behaviour. Further, exposure to the harsh realities of prison is thought to discourage former inmates from re-offending. These assumptions do not reflect most offenders’ reasoning, nor do they reflect the contexts in which most criminal behaviour occurs. Punishment of the type offered by prisons doesn’t meet the criteria for reinforcement of behaviour that one would associate with behaviour change; the punishment happens long after the behaviour, and is therefore futile [i] .  Firstly, it should be noted that among many inmates, especially young men, criminal actions, including public order offences, assault and petty theft, are carried out on impulse. Impulsive behaviour is often influenced by alcohol and peer pressure. Under these circumstances, deterrence is ineffective.  Secondly, empirical evidence indicates that it is the likelihood of being caught performing a criminal act, rather than the sentence for that crime, that deters potential offenders. If a potential offender believes he is more likely to be caught and convicted, he is less likely to engage in criminal behaviour. Meta-analyses such as the Cambridge Study on Deterrence [ii] have shown that the severity of a sentence only has a marginal effect on an offender’s decision to break the law.  In the light of these findings, deterrence can be seen as a matter of policing and detection, rather than a set of misleading assumptions based on an over-simplification of rational-actor theory.  [i] Andrews, D.A. &amp; Bonta, J., “Rehabilitating Criminal Justice and Policy” in Psychology, Public Policy and Law (2010, Vol. 16, No.1). Page 42  [ii] “Criminal deterrence and sentence severity: an analysis of recent research”, von Hirsch, A, and others