A German court convicted retired U.S. autoworker John Demjanjuk on Thursday of taking part in the murder of tens of thousands of Jews as a Nazi death camp guard, breaking legal ground that could pave the way for the prosecution of many low-level cogs in Hitler’s machinery of destruction.

The 91-year-old Demjanjuk was sentenced to five years in prison on 28,060 counts of accessory to murder — one each for the number of people killed at the Sobibor death camp during the six months in 1943 when he was convicted of standing guard there.