By Saturday, we knew that the American student Amanda Knox had changed her account of Meredith Kercher's murder three times, that she was sitting in her prison cell writing version after version of what had happened on the night itself, that she had a reputation as a heavy drinker with an active sex life, that she had posed on her website with a machinegun.

By Sunday we were reading interviews given to the press by the arrested suspect Raffaele Sollecito, in which he gave his own story, complete with admissions that he smoked cannabis and had a large collection of knives. By Monday, a report from the judge examining the case had been leaked, offering us a full rundown on the evidence uncovered by police, including a lurid description of the scene of the crime, written (or translated) in the language of the penny-dreadful: “With the door opened there was a chilling scene... the room was found in disorder with blood stains everywhere, on the ground and on the walls, and also under the duvet of the bed a foot could be seen.” So detailed was the judge's report that it even included the Vodafone number of the mobile phone found in the garden next to Meredith's house.

This is justice Italian-style, no holds barred, full disclosure, fact and speculation freely intermingled; the word “alleged” has been notable for its absence. This is the polar opposite of the much-criticised Portuguese system applied to the Madeleine McCann case, in which no details were officially issued and suspects, named by police, were legally forbidden to speak.

Neither case, however, has demonstrated the two prerequisites of a just legal process: an unbiased police inquiry and the presentation of untainted evidence in court. How any of the three suspects so far arrested in Perugia can expect a fair trial, should a case against them ever be brought, is almost impossible to imagine. Furthermore, the clear-headed analysis of evidence has already been polluted. As each new discovery is publicised and every new theory widely aired, the public pressure for action grows, and the hand of the investigating authorities is forced. Although the judge is meant to be wholly independent, with the task of weighing the police evidence against the claims of defence counsel, even he cannot expect to remain immune to the overwrought atmosphere in which his inquiries are held. Trial by press conference is not the best means of ensuring that justice is done - but that is what we are witnessing.

New witness 'saw Meredith suspects together'

Amanda Knox, Raffaele Sollecito and Rudy Guede were see at the house in Perugia where the American student died

Multimedia

• Murder in Perugia

BACKGROUND

• Meredith Kercher: Q&A

• New DNA not from Meredith suspects

• Timings crucial to Kercher murder investigation

In Portugal, the so-called code of secrecy has resulted in the deliberate manipulation of evidence. Sheltering behind the law, officials have briefed favoured journalists, allowing a barrage of damning allegations to be unleashed against Madeleine's parents. With little or no hard proof to sustain the charges, they have nevertheless turned a supposedly objective criminal investigation into an exercise in character assassination. The Portuguese authorities may argue that they are simply responding to accusations from the British media that they have botched the inquiry, but that is hardly justification for distorting the evidence.

There was a time when it might have been possible to claim that the British approach to criminal investigations avoided both these extremes. The laws of contempt kept a tight rein on premature disclosure of any evidence that could influence a future jury. They were best summed up by Lord Hope of Craighead, a Scottish judge (the rules have always been tighter north of the Border), who observed that it was “in the public interest that proceedings for the detection and punishment of crime should not be interrupted by the effect on the course of justice of publicity”. Once an arrest was made or charges brought, the tried and trusted (if often deeply resented) formula of “last night a man was being held in connection with the case” became the last word on the subject before a trial.

It is hard, however, to constrain the press in the hothouse world of international competition. These days newspapers exist in the age of the internet, when facts, sub-facts and downright inventions circulate freely and are instantly available online from news organisations in other countries whose freedom to publish is far wider than ours. Access to previous convictions, for instance, can be instantly gained through Google; references to royal figures whose privacy is protected by judge's orders in Britain can be picked up with ease on any number of foreign websites. And when readers are able to fill in the blanks for themselves through electronic means, the

press can sometimes feel they are operating with one hand tied behind their back.

Recent cases, such as the allegations of rape made in 2003 against a number of footballers in a London hotel, when lurid details were published in advance of a trial that then had to abandoned; or the case of the “Suffolk strangler”, where compromising information about a potential suspect was widely aired after he had been arrested, suggest that the boundaries of what is permissible are being stretched. The police, too, seem more prone to allowing evidence to leak into the public arena. Set against that, however, is the very real threat to newspapers that if they print material that allows a defence QC to argue that his client's case has been undermined and the trial has to be called off, the newspaper can be landed with the bill.

We are all, of course, breathless for gossip and, in the case of murder, we are insatiable. So used have we become to the immediacy of information, and to instant access to the latest revelations, that we have come to expect it as our right. But in most murder cases there is likely not only to be a guilty party but an innocent suspect as well. The law is there to nail one and absolve the other. Everything else takes second place to that.

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