"It does not have to be correct just because it is written there," he said.
Prosecutors, however, say they have documents which prove his Nazi background, including an SS identity card which shows he was posted to the death camp in Sobibor in 1943 and many witness testimonies.
Mr Demjanjuk's deportation was welcomed by observers.
Wolfgang Benz, head of the Centre for Anti-Semitism Research at Berlin university, said the case was about establishing whether Mr Demjanjuk was guilty, not exacting punishment.
"This is about guilt, about avenging a crime, about responsibility for a criminal act," he told told Deutschlandfunk public radio.
"Whether this old man who possibly is in a pathetic state spends his last years in a prison hospital or does not serve his sentence due to ill health, that's of secondary importance."
That opinion was echoed by Stephan Kramer, general secretary of the Central Consistory of Jews in Germany.
"I am not as naive as to believe that he [Demjanjuk] will spend even one day in prison. But we will get a discussion about justice in post-war Germany and how the justice system has dealt with Nazi crimes," he was quoted as saying.
Mr Demjanjuk arrived in the US in 1952 as a refugee, settling in Cleveland, Ohio, where he worked in the car industry.
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