In case you have missed the news, Oskar Groening is being tried for being accessory at Auschwitz. He's 93, admits his moral guilt but questions his legal guilt. He worked at the camp from May 1944 to June 1944; he was an accountant. He knew what was happening which was why he requested transfer after transfer.
There was an attempt to charge him in the 1980s; it failed. In 2005, he was interviewed for a well done BBC mini-series about the camp. He has been upfront about what happened and started speaking out when people denied the Holocaust happened. (And if you haven't watched the series, you should. In particular compare Groening to another guard who says the Jews deserved it).
I find the whole trial interesting for several reasons - why so long for the charge (is it simply a change in the law), and the question of punishment.