In 1970, reacting to criticism that Oz had lost touch with youth, the editors put a notice in the magazine inviting "school kids" to edit an issue. The opportunity was taken up by around 20 secondary school students who were let loose on Oz #28 (May 1970), known as "Schoolkids OZ". This term was widely misunderstood to mean that it was intended for school children, whereas it was a statement that it had been created by them.
One of the resulting articles was a highly sexualised Rupert Bear parody. It was created by 15-year-old schoolboy by pasting the head of Rupert onto the lead character of an X-rated satirical cartoon by Robert Crumb. The majority of the contributors were from public schools (in the UK sense of the term: elite non-state schools); as a result the humour was mostly an extension of the type of material familiar from undergraduate Rag Mags.
Oz was one of several 'underground' publications targeted by the Obscene Publications Squad, and their offices had already been raided on several occasions, but the conjunction of schoolchildren and arguably obscene material set the scene for the infamous Oz obscenity trial of 1971. In some respects it was a copy of (an earlier unrelated) Australian trial, with evidence and judicial instruction clearly aimed at securing a conviction, but the British trial was given a far more dangerous twist because the prosecution employed an archaic charge against (the editors) Neville, Dennis and Anderson—"conspiracy to corrupt public morals"—which, in theory, carried a virtually unlimited penalty.
The defence lawyer, John Mortimer QC announced at the opening of the trial in 1971 that “[the] case stands at the crossroads of our liberty, at the boundaries of our freedom to think and draw and write what we please” (The Times: 24 June 1971). For the defence, this specifically concerned the treatment of dissent and dissenters, about the control of ideas and suppressing the messages of social resistance communicated by OZ in issue #28. The charges read out in the central criminal court stated “[that the defendants] conspiring with certain other young persons to produce a magazine containing obscene, lewd, indecent and sexually perverted articles, cartoons and drawings with intent to debauch and corrupt the morals of children and other young persons and to arouse and implant in their minds lustful and perverted ideas” (The Times: 23 June 1971). According to Mr Brian Leary prosecuting “It dealt with homosexuality, lesbianism, sadism, perverted sexual practices and drug taking” (op. cit.).
The trial brought the magazine to the attention of the wider public. John Lennon and Yoko Ono joined the protest march against the prosecution and organised the recording of "God Save Oz" by the Elastic Oz Band to raise funds and gain publicity.
Dennis and Anderson were defended by lawyer and playwright John Mortimer (creator of the Rumpole Of The Bailey series) with assistance from Australian lawyer Geoffrey Robertson, while Neville represented himself.
The trial was, at the time, the longest obscenity trial in British legal history. Defence witnesses included comedian Marty Feldman, artist and drugs activist Caroline Coon, DJ John Peel, musician and writer George Melly and academic Edward De Bono. At the conclusion of the trial the "Oz Three" were found guilty and sentenced to hard labour — although Dennis was given a lesser sentence because the judge, Justice Michael Argyle, considered that Dennis was "very much less intelligent" than Neville and Anderson. Shortly after the verdicts were handed down they were taken to prison and their heads shaved, an act which caused an even greater stir on top of the already considerable outcry surrounding the trial and verdict.