CLEVELAND, Oct. 19, 2011 (UPI) -- Attorneys for John Demjanjuk, convicted in Germany of being a World War II Nazi war criminal, say they want to bring him back to the United States.

Lawyers for the 91-year-old former Cleveland-area man contend prosecutors withheld documents that could have helped his defense, The (Cleveland) Plain Dealer reported Wednesday. They have requested that U.S. District Judge Dan Aaron Polster set a hearing to determine why prosecutors' failed to turn over a 1985 FBI memo about a Nazi identification card linked to their client.

The defense attorneys say the ID card likely could have been faked by Soviet secret police and the failure of the government to turn it over to them had an "incalculable" impact on his case.

The newspaper said federal prosecutors filed documents Tuesday night in federal court in Cleveland outlining what they indicated was an inadequate FBI investigation concerning the card and maintaining they had not been informed about the FBI's monitoring of Demjanjuk.

Demjanjuk was convicted in May of being an accessory in the deaths of more than 28,000 people at a Nazi death camp where he was a guard.