I've explained before that free will is superstitious nonsense. The reasons for a person's actions are determined by factors outside of their control - this is a logical necessity. And so the rational way to treat crime is as a sickness with causes, rather than a sin of volition.
Put me in charge of parking fines in Auckland City, and I can make a statistically significant number of drivers pay for parking - by doubling the fines. Nothing else will have changed, except for me upping the fines, and that will change their behaviour. External factors.
It's fairly well known that the book Freakonomics claimed that crime rates in the US markedly dropped as a result of legalised abortions. 20 years later, there was a generation of unwanted 20-year-olds born to impoverished young single mothers who didn't exist to join gangs and smoke the marijuana like a cigarette. Crime, which had been a growing concern in the US, plummeted.
The Independent is now reporting that crime has dropped due to leaded petrol being banned. Lead had been associated with minor brain damage in children exposed to it - potentially resulting in higher rates of criminal behaviour as adults. The UK was one of the last developed countries to ban lead in petrol, and it's the last to see a significant drop in crime.
To be concerned more with the long-term causes of crime than the immediate prevention and punishment of criminals in the short term is typically a left-wing political perspective. Right-wing politics are often identified with harsher sentencing and more police powers - whether due to the ideology of the politicians or the simple practicality of an easily grabbed senior-citizen vote.
Unfortunately, people have very short memories, and policies that have long-term reductive effects on crime are seldom appreciated in the form of popular political support. In other words, if you're asked what you're going to do about crime, and you say you'll remove its causes 20 years from now and the other guy says he'll make "life mean life", you'll lose, and 20 years later, crime won't have dropped off.
No more wall candy, people.