It is unusual for France and Britain to sing in chorus. But on both sides of the Channel one can hear the same refrain: "Crime is out of control. The criminal justice system is failing. The courts are feeble. They [the British/ French] do things better over there" (pointing across the Channel).

In Britain, the Commissioner of the Metropolitan police, Sir John Stevens, says that our "adversarial", Punch and Judy, defence v prosecution system of trials gives too much advantage to the defence. Witnesses are being intimidated and bullied in court. Juries are unreliable. Too many criminals are walking free. Some British experts suggest that, for complex cases at least, we should import the French system of "inquisitorial" justice, in which an independent magistrate investigates all the evidence, both incriminating and exculpating, before a case goes to court.

In France, voices from the right are calling for the juges d'instruction, or investigating magistrates, to be abolished. The French system is archaic, secretive, slow and inefficient, they say. It would be better to move to the "Anglo-Saxon" system of adversarial justice, which is quicker, more open and more accountable.

So that is agreed then. The British do it better, according to the French. And the French do it better, according to the British. Not all of the British. The parents of Caroline Dickinson, the Cornish schoolgirl murdered in Brittany in 1996, might not agree. The botched investigation of her killing – and that of several other British women in France in recent years – can be blamed in part on the failings of the French inquisitorial system.

Geoffrey Boycott might also give you a lecture on the dangers of trying to blend two systems, rooted in profoundly different national cultures and centuries of separate, judicial traditions.The England batsman- turned-commentator tried, ill-advisedly, to import the British adversarial approach to a Provençal court-room a couple of years ago, when he was convicted of assaulting a woman friend in Antibes. The result was utter confusion, as if he had attempted to bowl a googly in a game of pétanques.

What are the differences between the two systems? In the British system, and also, broadly speaking, the American system, the police and prosecution gather information likely to convict the suspect. The defence gathers information likely to acquit the defendant. Arguments between the two, and the examination of witnesses, are conducted in open court, and refereed by a judge. The winner is decided, in most important cases, by a jury of ordinary citizens.

In the French system, also adopted in many other continental countries, all criminal cases are investigated by an examining magistrate. He or she is independent of the government and the prosecution service, but works with the police. Much of the "trial" of the evidence goes on, in secret, during the investigation (confrontations between witnesses; recreations of the crime). The final report of the investigating magistrate is supposed to contain all the evidence favourable to both defence and prosecution.

The investigations are frequently long – two years in straightforward cases is normal – but trials are mostly short. Witnesses are called and the evidence is rehearsed in court, but lengthy cross-examination in the British/American style is rare. In the courts of assize, which hear serious criminal cases, there are nine jurors, who sit with three professional judges: other criminal cases and appeals are heard by panels of judges alone.

In France, as in Britain, the defendant is innocent until proven guilty but, in practice, there is a strong presumption of guilt if an examining magistrate, having weighed the evidence, sends you to court.

It is important to remember that this system grows from a legal framework and culture very different from our own. There is no right of habeas corpus in France. Investigating magistrates have a right (within limits) to imprison suspects for lengthy periods without trial, which can be a handy way of extracting evidence. Suspects can admit or deny their guilt, but their plea makes little difference to the nature of the investigation and trial.

Critics of the French system in France fall into two groups: those who think that investigating magistrates are too powerful and those who think they are too weak or ineffectual. Part of the problem is one of resources. There are only 562 investigating magistrates in France. There are 60,000 investigations in progress at any one time; on average, each magistrate is investigating over 100 cases simultaneously.

Much of the leg-work is done by the police (in towns) or gendarmerie (in rural areas), but relations between the judges and police are not always good. One of the arguments against the examining magistrate system is that it demotivates the police and downgrades both old-fashioned and hi-tech forms of detection – from Maigret-style clue-hunting and intuition to genetic data banks and DNA tests. It puts the emphasis instead on what judges know best: interrogation and mind-games.

The investigating magistrates have done excellent work in the last 10 years in uncovering corruption in the highest levels of French business and politics (where interrogation and mind-games are crucial). They have been successful in puncturing the arrogance, clientelism and impunity with which most French politics used to be conducted. (President Jacques Chirac is a survivor of the old attitudes, but maybe not for long.)

The examining magistrate system is less obviously sensible when it deals with ordinary, decent, or indecent, criminals. It slows and chokes the system; fills French jails with people who have not been charged; and encourages a quite unnecessary secrecy in the conduct of criminal investigations which can be a blanket for laziness and incompetence.

It is difficult to see the advantage in importing investigating magistrates to the UK to deal with the bulk of criminal activities, though there may be a case for introducing a class of independent judicial investigators for complex cases of fraud and corruption. In France, conversely, there may be a good case for freeing the police and gendarmerie from judicial control in their investigation of a wider range of "ordinary" crimes. This would, in turn, lighten the workload of the juges d'instruction to deal with political and financial and the more complex offences, such as organised crime.

The problem in both cases would be the "Geoffrey Boycott objection". It may seem simple to borrow part of one judicial system and graft it onto another. In reality, the two systems spring from different cultures, different histories, different psychologies. It might be just as easy to grow fine wines in Yorkshire or to persuade the French to eat Yorkshire pudding.

indyparis@compuserve.com