FOR MEDIA lawyer Campbell Deane the moment motor racing boss Max Mosley's privacy case against the News Of The World tipped into high farce was when the paper's reporter outlined why he felt the story was in the public interest.

Says Deane: "He claimed that a criminal offence had been committed. Namely, that the dominatrix had caned Mosley so hard they had to put a plaster on his arse."

From that point onwards the NOTW case looked desperate, Deane believes, a position that only worsened when "Woman E", the alleged prostitute who was supposedly paid by the paper secretly to film Mosley taking part in a sado-masochistic orgy with five prostitutes, failed to take the stand in the paper's defence.

Deane, like most media lawyers and indeed most journalists not working for NOTW owner Rupert Murdoch's News International, believes the most salacious, and perhaps controversial, of Sunday papers is heading for an expensive fall. The case has centainly been enough to worry some editors - Deane says he has been consulted by two in the past few weeks about the emerging law.

In exchange for the invasion into his private life - as Mosley sees it -he is seeking punitive damages, meaning an amount of money designed to deter the NOTW, and indeed any paper, from gathering information about somebody's private life when it is not in the public interest to publish.

Although no-one is yet brave enough to venture forth with a potential damages figure, and leading Scottish editors are reluctant to discuss the case until the verdict is announced, the effect on the media has already been marked. Despite the fact punitive damages are not awarded under Scottish law, the feeling is that the case will change the relationship between the media and its subjects. Privacy could become, as one lawyer put it, "the new libel".

Although Madeleine McCann "aguido" Robert Murat's £600,000 payout last week from 11 newspapers after successfully suing for the separate offence of defamation, editors are being forcefully reminded to think longer and harder about what stories papers can and should run.

Privately, several senior newspaper executives now feel the Mosley case, and the effect it will have in firming up a still embryonic privacy law in the Scottish and English courts, will force editors to consider the consequences of foraging through someone's private life in search of a scoop.

In 2004, model Naomi Campbell won a landmark breach of confidentiality case against the Daily Mirror, after the newspaper published photographs of her which were held to be in breach of her privacy.

The Mosley case marks another milestone in the still-evolving field of privacy law. Based on article 8 of the European Convention of Human Rights, which states an individual has a right to a private life, the courts have been increasingly taking the view that the public interest must be greater than the potential harm caused to the subject of a story by publication.

Austin Lafferty, another leading media lawyer, says NOTW editor Colin Myler simply went too far with the Mosley story: "I am not myself a fan or a practitioner of kinky sex but I do have a degree of sympathy for Mr Mosley. My personal foible is Batman comics but I wouldn't want to be pictured at a Batman theme party."

Star publicist Max Clifford, who made his name selling sex and other scandal stories to the red-tops, told the Sunday Herald that such a law would be a good thing: "We are getting closer to a privacy law in all but name. It is good to have a free press, and I've broken more stories than any of them, but the subjects - David Mellor the Conservative minister, for example - were all in positions of genuine public interest.

"Now it's all sensation and no substance and the public realise that. The more irresponsible papers are the harder they make it for themselves. I mean who is Max Mosley? No-one had really heard of him before this."

However, BBC Scotland radio presenter and journalist Tom Morton - who was himself the subject of salacious and fictitious allegations about his private life published in The Sun - urged a note of caution.

Despite considering suing the Press and Journal, which repeated the allegations unchecked, and without contacting him, Morton feels uneasy about any developing privacy law.

"I've worked for the red-tops, and they are like a wild animal, you can't expect them to act reasonably. As a journalist myself I'd have to look very closely at the details of any emerging law. Although I think everyone has the right to a private life, I always realised there would be a price to pay if you are a public figure and are on the radio."

There is no guarantee that any emerging privacy law will be used correctly. Alistair Bonnington, BBC Scotland's head of legal, says the making a documentary about Glasgow Sherriff Court showed the way privacy law could be abused to the detriment of good journalism.

Bonnington says the team worked with a woman whose partner was charged with a number of crimes. They interviewed her over a period of days, filming her experience of the justice system. But after filming was over, the woman changed her mind and decided she didn't want to be included in the film.

When the BBC refused to acquiesce, she applied for legal aid and won a court order that delayed broadcast of the piece for eight months on the grounds the documentary had invaded her privacy. When the piece was eventually broadcast, her face had to be pixilated out.

Says Bonnington: "The courts accepted her argument that she was very drunk when signing the consent forms and throughout all the filming."

For Deane, whatever the eventual outcome of the Mosley case it will not have too alarming an effect on the way the media works. But that, he warns, could be just around the corner.

"This law is evolving all the time and unlike the laws governing libel editors do not yet know where they stand, what they can do and what they cannot do. That will only come when Joe Bloggs, someone with no public profile at all, tests the principles made in cases such as the Mosley one, and brings an action. Then we will see what the privacy law will really mean."