A high-profile US obscenity trial has been put on hold after it emerged that the top federal judge hearing it had posted sexually explicit material on his personal website including footage of a semi-naked man cavorting with a sexually aroused farm animal.

Other material found on Judge Alex Kozinski's site, which has now been blocked, included a photograph of nude women on all fours painted to look like cows and another of a young man giving himself fellatio.

Mr Kozinski is hearing the trial of Ira Isaacs, a 57-year-old Los Angeles-based film maker, who faces up to 20 years in jail and a huge fine if convicted of selling criminally obscene fetish videos depicting bestiality and defecation.

But his trial at the Los Angeles Federal Court was put on hold just hours after it opened after an LA Times report about obscene material posted online by Judge Alex Kozinski. The judge agreed to the prosecution's request for a 48-hour delay so that the Justice Department could look into possible issues of prejudice in the case.

Mr Kozinski, 57, is a larger-than-life character who is chief judge of the 9th Circuit Court of Appeals, which has jurisdiction over nine western states. A judicial conservative who has been mooted as a possible candidate for the Supreme Court, he is also a noted advocate of free speech: he is most famous for having personally switched off the filters blocking access to internet pornography from 9th Circuit computers.

According to the LA Times, the material on Mr Kozinski's website could only be accessed by those who knew to type in the name of a subdirectory to which there was no visible link. Apart from family documents and photographs there were also images of masturbation and public sex as well as a "slide show striptease featuring a transsexual and a folder that contained a series of photos of women's crotches in snug-fitting clothing or underwear".

Mr Kozinski told the newspaper that he was unaware that photographs posted on his personal site could be viewed by the public and that he had removed the pictures. He was also quoted as saying that he did not believe any of the images on the site qualified as obscene.

“Is it prurient? I don’t know what to tell you,” he said. “I think it’s odd and interesting. It’s part of life."

But in an interview with the newspaper he defended as humorous a picture showing two women sitting in a cafe with their skirts hiked up to reveal their pubic hair. Behind them is a sign reading "Bush for President".

"That is a funny joke," Mr Kozinski said.

Unfortunately for the judge, there were also said to be more than a dozen copyrighted music tracks listed on the site in MP3 format from artists including Johnny Cash, Bob Dylan and Weird Al Yankovic.

Mr Kozinski will now come under intense pressure to excuse himself from hearing the trial of Mr Isaacs, whose films include such titles as "Gang Bang Horse ’Pony Sex Game,’”,“Mako’s First Time Scat,” and “Hollywood Scat Amateurs No 7".

But he is unlikely to go down without a fight. His defence is likely to be that he was simply using the website server to store material sent to him: it was not meant for public transmission.

Mr Kozinski was born in Romania, the son of Holocaust survivors, and came to America at the age of 12. Six years later, in 1968, he won a date on an episode of the TV show “The Dating Game" after greeting the contestant with "good afternoon, flower of my heart”.

He builds his own computers, describes himself as an authority on snowboarding and has written video game reviews for the Wall Street Journal.

The judge often puts in 80-hour work weeks and is infamous for sending 3am e-mails to the recent law school graduates who successfully win coveted one-year appointments as his law clerk.

“He has an outlandish personality for a federal judge,” said former clerk Harry Susman, a Houston lawyer. “He has a great sense of humour.”

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