Demjanjuk, 72, was stripped of his US citizenship in 1985 and extradited in 1986 to Israel, where he has been sentenced to death. His case is the subject of an appeal to the Israeli Supreme Court. The court of appeals said it could overturn Demjanjuk's extradition if it learns that prosecutors had failed to give his lawyers information which would have helped them defend him. Demjanjuk's family has argued that a man named Ivan Marchenko, not Demjanjuk, was the real 'Ivan the Terrible' - the guard who operated the gas chambers in Poland's Treblinka death camps. Some 850,000 Jews died at Treblinka in 1942 and 1943.