I think only one actually went to trial. Helmut Patzig, who sank the hospital ship *Llandovery Castle* and then MG'ed those in the lifeboats. However, Patzig was "unable to be found" at time of trial (apparently he was living in Danzig, which by 1921 was in Polish jurisdiction, not German) and thus his two watch officers, Dithmar and Boldt, were put in the dock in his place.

It's not in the book, but it looks like several others answered to an inquiry of sorts by the tribunal and had the charges dismissed before trial for lack of evidence: sort of a grand jury phase, if you will.

I believe Walter Forstmann of U-39 (the second ace of WWI behind von Arnauld) was one of these, accused by the Italians on charges I haven't been able to find. Considering even the British didn't list him as a criminal, it's not surprising he was sent on his way.