It's not the violence of the police that gives away their nature, it's the systematic compulsive Bart Simpson-style lying. They could be caught on film battering someone with a cricket bat, and in seconds they'd issue a statement that went, "I didn't do it. He was already dead when we got here this morning. He was a commander with the Taliban. He pointed a nuclear missile at me. He shouted, 'I'm going to blow up the universe'. He's the Devil. That's it, we've checked his DNA file and he's the Devil."

A similar attitude was evident before the recent G20 protests, when the police, not individual policeman but spokesmen for the police as a body, issued endless statements that suggested they were getting pumped up like American wrestlers before a television battle. If they'd had a couple more days they'd have got a chief inspector in a vest to flex his biceps, lean into a camera and growl, "Now listen up, April 1st is gonna be Judgement Day. I gotta message for you protest punks, when I'm through it ain't gonna be climate change botherin' you, it'll be the change in the shape of yo ugly ass. Grrrrrr."

Every time someone dies as a result of police behaviour, from Hillsborough to Stockwell to the G20, these creative lies pour forth, before crucial footage goes magically missing from their records. So maybe it would be fair if criminals were allowed a similar privilege.

After a bank robbery they could hold a press conference, and announce they had confidential information that the bank was laundering money to the IRA, and Mrs McGinty the bank clerk had vaulted over the safe carrying what appeared to be a flame-thrower, so faced with a split-second decision the gang had no alternative but to tie her to a chair and blow up the safe.

Despite the lies, little action is taken against them and senior politicians make speeches such as, "We must not forget the police do a magnificent job in horrendously evil circumstances, and to stop them from lying would be to remove one of their most valuable tools in the fight against those people who want to burn down your house."

And then they're investigated by another branch of the police, which has as much chance of producing an impartial outcome as if the FA allowed all Manchester United's matches to be refereed by Alex Ferguson.

This is why the issue is about more than individual "hot-headed" policemen. No other profession would be protected like this. If a chemist went berserk, you wouldn't get the head of Britain's chemists making a statement that "The pharmacist observed Mr Winthrop lurking suspiciously by the Lemsips, and felt he had no choice but to administer six shots to the head from his.22 calibre pistol in order to protect the public. Obviously he regrets the loss of life incurred now it has been established the deceased was seeking a remedy for his cold, but it would be quite wrong to criticise this brave chemist for carrying out his duty."

It seems the police are trained to behave like this, which is why they've been like it for decades, with the difference now that with modern gadgets their actions get caught on film. Which is why the civil liberties groups are wrong, and the police are right about the need for more and more CCTV cameras. We do need more of them, the only thing is most of them should be pointed at the police.