I taught the law

Mr Toad was jailed for "cheeking the police". The same thing nearly happened last month to Henry Louis Gates Jr, a professor at Harvard University.

In a case that convulsed America, James Crowley, a police sergeant, arrested Gates on his doorstep after the professor demanded to see the officer's credentials. Mr Toad compounded his felony, according to the judge, by "being green". Gates' pigmentation had a similarly exacerbating effect: he is black.

Gates returned from holiday to find his front door had warped. As it would not yield to shoving, he let himself in around the back. Meanwhile, an observer called the cops to report what she mistook for a burglary. The policeman who came to check assumed that Gates was a burglar and, when the professor threatened to make a complaint, declined to give his name or badge number and represented his interlocutor's indignation as "disorderly conduct". Gates responded with accusations of racism.

Injudiciously responding to a question about the incident at a routine press conference, Barack Obama said that the policeman had acted stupidly. Politicians on the authoritarian Right seized the chance to deride his racial over-sensitivity and denounce the President for failing to support law and order.

By raising the spectre of racism, I think Gates missed the point. Whatever his other defects, the arresting officer had a good record on racial issues. The caller who alerted the police did not mention that the "intruder" was black.

Racism is still rife in many US police forces, but is probably not a big problem in Cambridge, Massachusetts, where Gates' arrest took place. If the officers victimised the professor, their prejudices are more likely to have been anti-intellectual than anti-black.

I can sympathise with Gates because, notoriously, I was the victim of a similar incident a few years ago in Atlanta, during the annual conference of the American Historical Association. I was assaulted by a policeman and briefly jailed, ostensibly because I had crossed the street at an unauthorised place.

The real reason for the policeman's ire was that I asked to see his badge, which, with the rest of his uniform, was concealed beneath a capacious bomber jacket. In the US, the police demand and expect deference from the public. Question officers' authority and you trigger their tempers. The mean streets are never far from Main Street and the line between civility and savagery is easily transgressed.

The real problem the Gates case raises runs deeper than racism: it is a matter of the relationship between the police and the rest of society. The way police officers generally understand their role seems grossly distorted. It is hard for them to retain a sense of solidarity with citizens outside the force, partly because they need to cultivate a strong esprit de corps to be able to do their job. From an officer's point of view, members of the public are often disappointingly unhelpful.

We are reluctant and unreliable as witnesses; rambling and troublesome as complainants; ignorant and irresponsible in crime prevention; and heedless and insouciant in infringing the many petty regulations the police are obliged to enforce. It is easy for them to forget that they are supposed to be on our side.

Their top brass and civilian masters neglect to remind them that their job is public service and that they exist to help their fellow citizens, not alienate them. Every time a decent, useful, law-abiding person suffers from the arrogance or indiscipline of the police, the bonds of collaboration weaken. Social peace depends on that collaboration. When the force loses sight of its proper goals, the only winners are criminals and terrorists.

In Britain, the failure of police training seems at least as bad as in the US. The killing of Jean Charles de Menezes was as evil as any excess of trigger-happy zeal, and the death of Ian Tomlinson, an innocent bystander who happened to wander into the area in which a lawful demonstration was taking place, is bound to undermine every decent person's confidence in the thin blue line.

I was shocked to hear a police spokesman defend the savage way the force handles demonstrators by claiming that the primary responsibility of the police during a demonstration is "to protect property". That is a constant obligation of the police, but surely their special responsibility during demonstrations is to defend demonstrators' rights - which includes co-operating with the organisers to deal firmly but honourably with subversive and violent infiltrators.

The police desperately need to be re-educated in humanity. Recent graduate-recruitment schemes should have a beneficial effect in coming years, but the force's non-graduate majority are not much better educated than the criminals. If we believe in the moral value of education, we should be unequivocal in demanding a better-educated force and we must be flexible in helping to make it possible.

Universities should offer to help by giving all police officers the chance to be classmates with their fellow citizens. Professor Gates should not have been in Sergeant Crowley's lock-up, but maybe Crowley should have been in Gates' class. Secondment to suitable university courses in the humane disciplines could and should be a compulsory part of police training.