Experts say Obscene Publications Act now 'makes no sense' after jury rejects claims that mail-order material was capable of 'depraving and corrupting'

It was the law used in the controversial prosecution of Lady Chatterley's Lover. Now the Obscene Publications Act, which came into force in 1959, appears to be on its last legs.

On Friday, in one of the most significant cases of recent years, a London jury rejected prosecution claims that gay pornography depicting acts that are legal between consenting adults were capable of "depraving and corrupting" those who watched them on DVDs.

The case, at Southwark crown court, threatens to have implications far beyond the acquittal of pornographer Michael Peacock, who ran a mail-order business and had been targeted by an undercover vice officer.

Officials at the British Board of Film Classification, as well as police officers involved in prosecuting obscenity cases, have admitted that the current laws on what is obscene may require a major rethink.

The act was used, unsuccessfully, against Penguin Books for publishing Lady Chatterley's Lover, when a jury was asked whether it was the kind of book "you would wish your wife or servants to read". It was deployed more successfully in 1971 against Oz magazine, although that prosecution was overturned on appeal, and unsuccessfully again against the book Inside Linda Lovelace, which led to the police view that it was almost impossible to prosecute for obscenity in cases of written representations of sex.

The latest case – which saw a jury take two hours to return not guilty verdicts – comes amid growing concern that Britain's obscenity laws, which have multiplied in recent years with new laws on the possession of "extreme pornography", are contradictory, ill-defined and illogical.

While the act – used to prosecute publishers rather than those in possession of proscribed material – has only been used in 71 cases in the last year, its social impact is far more wide-reaching, with the Crown Prosecution Service using it to advise film censors and others on what they believe a jury would find obscene.

Peacock, who advertises online, had been approached by an undercover officer seeking to buy videos depicting so-called "water-sports" and other acts that, while legal in consensual sex, appear on the CPS list of acts it advises may be prosecuted for obscenity.

The prosecution had suggested that the Peacock's customers were not aware of the explicit content. Peacock said customers "asked me for specific titles or niches, and knew exactly what they were getting". The jury decided that the audience could not be "depraved and corrupted" by material it had actively sought out.

Peacock's solicitor, Myles Jackman, said: "The jury's verdict is a significant victory for common sense suggesting that the OPA has been rendered irrelevant in the digital age. Normal jurors did not consider representations of consensual adult sexuality would deprave and corrupt the viewer."

Most obscenity prosecution now takes place under the auspices of newer "extreme pornography" legislation which requires a lower level of proof – possession – although still requires that a "reasonable person" should believe that what is being depicted is both real in its representation and physically harmful.

Feona Attwood of Sheffield Hallam University, who lectures in sex, communication and culture, and who attended the trial, said: "I think the law does not make sense. All the evidence that was heard was about whether the material had the ability to harm and corrupt. The question now is, what does that actually mean? What is significant is that the jury understood [the issues at stake]."

Attwood, like others experts in the field, believes that the law has been overtaken by new understandings of the way in which people think about sexuality and the depiction of sex including whether a process actually exits that leads to "moral corruption". Others who have been deeply critical of the attempted prosecution – which could have seen Peacock jailed for up to five years if he had been found guilty of the six charges – include solicitor and New Statesman legal blogger David Allen Green.

Writing during the case he said: "Obscenity is a curious criminal offence, and many would say that it now has no place in a modern liberal society, especially when all that is being portrayed in any "obscene material" are the consensual (if unusual) sexual acts between adults."