Weekly magazine Focus reported that although 23 witnesses had been named, and five from Russia and Ukraine had been expected, they are long-dead.
Demjanjuk is accused of assisting in 27,900 murders during his time as a guard in the Sobibor concentration camp in what was then Poland, during 1943.
His defence lawyer Günther Maull told the magazine witness statements had been produced, but added, “The men were questioned 30 years ago – at least in part in the Soviet Union and possibly under pressure. Whether their statements have any value as evidence is questionable.”
Demjanjuk emigrated to the USA after the end of the war, and fought extradition to Germany. His family argued that his ill health should preclude a trial.
He was sentenced to death by an Israeli court two decades ago after he was convicted of being the feared death camp guard known as "Ivan the Terrible" who would hack at naked prisoners with a sword and inflict cruel and sadistic punishments.
That ruling was overturned in 1993 when statements from other guards identified another man as "Ivan."