John Demjanjuk, an accused Nazi concentration camp guard and war criminal, arrives in Germany to stand trial for his involvement in the murder of 29,000 Jews at Sobibor. Born Ivan Mykolaiovych Demianiuk in the Ukraine, he fought for the Soviet army against the Nazis and was captured in the Crimea.
Later Demjanjuk was recruited with other Soviet POWs to work for the Germans. He is accused by the German government of serving as a concentration camp guard, but Demjanjuk has in the past argued that he joined the Russian Liberation Army which, under the command of Andrey Vlasov, fought on the side of Nazi Germany against the Soviet Union.
Demjanjuk had previously been identified by Israeli Holocaust survivors as "Ivan the Terrible," a particularly notorious and brutal guard at the Treblinka concentration camp. He was convicted in an Israeli court in 1988 of being "Ivan the Terrible" and committing crimes against humanity, but the Israeli Supreme Court overturned the verdict based on evidence that he was the victim of mistaken identity — that while he may indeed have been a guard at Nazi concentration camps, he wasn't "Ivan the Terrible."
German prosecutors will adopt a different legal strategy. Instead of trying to prove that John Demjanjuk was guilty of committing any particular crimes, they will argue that simply being a guard at a concentration camp makes Demjanjuk an accessory to the major crimes committed there. The German prosecution of John Demjanjuk is sharply criticized, even by Germans.
It's almost certain that if John Demjanjuk worked as a guard at Sobibor or any other concentration camp (and the evidence that he did is debatable) then he was guilty of something. However, the government has a responsibility to demonstrate that a person is guilty of specific crimes in order to punish them. Ironically, one of the crimes of the Nazi government in Germany was to ignore that principle of the rule of law.