Deterrence

One of the most fundamental issues in the debate about crime and punishment lies in the part played by deterrence. We can all understand deterrence: at home, at school, in my working life, I was always aware that unacceptably bad behaviour would have unpleasant consequences for me. As a simple example I am so anxious to avoid a wheelclamp that I am meticulous about where I park. It isn't worth the risk, in my view.
Unfortunately, for someone to be deterred, he needs to have the ability to make a rational assessment of the pros and cons of his actions, and that ability is missing from the majority of the people who appear in my court. Many politicians and journalists simply fail to grasp this basic fact, and that's why we see so much nonsensical law making, that plays well in the pub, but has not the least effect on offending.
Cannabis is now class B rather then class C. This has the effect of increasing the potential penalties, but does anyone, even the most rabid hanger-and-flogger, expect that this will change the behaviour of pot smokers? The penalties for importing and trading class A drugs are awesome, but the amount of the stuff on the streets shows a steady increase. The same applies to so much criminal and antisocial behaviour - adjusting penalties doesn't seem to make a lot of difference when a young man (it usually is a young man) high on drink or drugs kicks off and attacks someone or something. You could make the same point about drink-driving; the penalties are severe, and there is a minimum sentence prescribed by law that can devastate the life and career of some people - nevertheless, as I type this there are thousands of over-limit drivers wending their way home from the pub.
Not simple is it?