Lukas Barth / AFP - Getty Images

The bed of defendant John Demjanjuk is pictured ahead of another session of his trial on May 4 in a courtroom in Munich, southern Germany. 91-year-old Demjanjuk, who is alleged to have been a Nazi camp guard, has been on trial since November 2009.

AP reports: John Demjanjuk's lawyer assailed Germany's prosecution of the 91-year-old on Tuesday, arguing that investigators have failed to offer concrete evidence of his involvement in Nazi war crimes and have been inconsistent in their efforts to pursue suspects.

Demjanjuk is charged with 28,060 counts of accessory to murder for allegedly serving as a guard at the Sobibor death camp in occupied Poland. He denies the charges.

Demjanjuk, as he has for much of his trial, lay in a bed wearing sunglasses during the proceedings. Read more.