Yes, I think he should go to jail. He was a willing participant in one of the worst atrocities of WW2.
There has been a myth developed about the Holocaust and the Nazis in particular, over the years, and it goes something like this :::
" Well, its not the German people who are at fault, it was just those horrid Nazis and the Gestapo that were to blame "
Wrong, wrong, wrong.
As was demonstrated by an excellent BBC documentary of a few years ago, about the rise of of antisemitism in Germany, many 10,000's or more, of quite ordinary Germans wholeheartedly embraced the Nazi line and willingly shopped their Jewish colleagues and neighbours to the authorities. ( if anyone can help with the title of that documentary, on BBC Two, I would be most obliged )
There is no doubt Groenings's guilt, as he helpfully incriminated himself during BBC documentary in 2005.
May he rot in whatever Hell he is going to. I couldn't care less !