The public is not daft,” says the refreshingly blunt Louise Casey, government crime adviser. Too right. We see ministers demanding tougher sentences and instructing earlier release. We see police forces spending ten times more on PR (what they want us to know) than on freedom of information (what we want to know). We wonder whether blokes on community sentences will wear Ms Casey's fluorescent “Convict!” jackets, like some kind of boy band, or will call in sick to skip the gig. And some of us wonder why one stark fact is missing from almost every review of criminal justice, including Ms Casey's - that the people who have most reason to fear the police no longer do so. When criminals don't fear the law, we are all in trouble.

Politicians seem far more interested in why the public's fear of crime is so high than in why miscreants' fear of the law is so low. Years of being told by academics that fear of crime is as important as crime itself seems to have made them determined to convince us that crime statistics are improving. But are those of us who doubt them wholly irrational?

Perhaps not. Stranger-murder - long used by many US police forces to track the underlying level of violence in society, but not separated out by the Home Office until The Times made a freedom of information request - has risen by 14 per cent since 1997. Violence seems to be becoming more vicious, with some accident and emergency doctors seeing more victims of stabbings. Many are teenagers. But the British Crime Survey, routinely trotted out to support claims that violence is down, doesn't include victims under 16.

So the 14-year-old boy stabbed in Southwark, South London, on Tuesday afternoon after a row with a group of youths will not register.

The boy was airlifted to hospital and, thankfully, looks likely to pull through. He was lucky - if you can call it lucky to have a narrow escape from death at 5pm on an ordinary London street. Every time a child is stabbed, police accuse the press of stoking up fear. But I don't want police who sound complacent, I want them determined to root out every last thug from every last bolt hole.

The day before the stabbing in Southwark, I had lunch with a friend who had been a prosecutor in 1980s Manhattan when gang crime was at its height. She speaks about the extraordinary success of the New York Police Department in an utterly matter-of-fact way. Their main weapon, she says, was information - who did what, where and when.

Witnesses who were hauled in were often so impressed by the team's knowledge that they would spill the beans. They also knew without doubt that the sanctions would be serious. New York was not squeamish about punishment. Now that London looks more like 1980s New York than New York itself, you might think that people would want to borrow the ideas that got the thugs running scared.

Yet Boris Johnson's proposal for “crime mapping” is meeting enormous resistance. The Metropolitan Police have long claimed that they map the streets, just as Rudy Giuliani did. But they won't publish the information.

Mr Giuliani used his data to make public comparisons of the performance of his commanders and tp hold them to account. He had no qualms about firing those who fell behind, or shipping them off to East Podunk. This made them phenomenally effective. British police, on the other hand, seem reluctant to sneak on each other. Even the bold Louise Casey, who wants police to report their actions to local monthly meetings, doesn't dare to suggest that citizens should get their hands on the data.

The squeamishness of British justice policy was neatly captured in last weekend's report by Professor Sir Al Aynsley-Green, the Children's Commissioner. On one page he spoke of his shock that so many British children live in fear. On another he expressed horror that so many children are being locked up. He appeared to see no contradiction between wanting to protect the majority while excusing the minority.

Yet some children are also thugs. However deprived their backgrounds, we cannot make them immune from the consequences of their actions. Many of them are kids who got away with playing truant at school; who were given a warning, which they saw as meaningless, for carrying a knife; who waited outside the magistrates' court to see if the witness would turn up, so that they could attend if he did, scarper if he didn't.

The “conveyor belt to crime” does not start in jail. It starts the first time that the authorities let children get away with something that they should not have done.

This does not mean that jailing youths is an easy decision. The sotto voce row between Ed Balls and Jack Straw over the future of the Youth Justice Board reflects the genuine difficulties of knowing how to punish youngsters without further entrenching them in a life of crime.

The choice between custody and rehabilitation should be an utterly false one. Custody should keep offenders off the streets and help them into a better future. But Britain's appalling record on rehabilitation means that the system stumbles from harshness to leniency and back, emboldening criminals and eroding public faith.

Right now, teenagers who carry knives seem more frightened of each other than of the law. We can't change that with adverts, only with police whose pensions depend on eradicating knives. Government must stop giving conflicting signals.

Yesterday in the Commons, Nick Herbert, the Shadow Justice Secretary, attacked the early release of violent criminals who are getting out of jail before their victims expect it, with no warning. “With this appalling policy”, he said, “comes a human price.” We all pay an enormous price for a system in which wrongdoers make a mockery of the law. That is daft. And criminal.

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