When a 100-year-old former concentration camp guard appears in court on Thursday charged with involvement in mass murder, he will become the oldest person ever tried in Germany for Nazi-era crimes.

Between 1942 and 1945, the suspect, solely named as Josef S., is accused of "knowingly and voluntarily" helping in the death of 3,518 detainees at the Sachsenhausen concentration camp in Oranienburg, north of Berlin.

Aiding and abetting the "death by firing squad of Soviet prisoners of war in 1942" and the murder of inmates "using the toxic chemical Zyklon B" are among the charges leveled against him.