It's kind of strange, that there were a bunch of Death Eaters who were able to escape punishment. Some of them claimed to be under the Imperius Curse.
However, it's kind of easy to check just by giving them the Veritaserum and asking whether they were truly under the curse or not.
Maybe unrelated thought. It looks like Death Eaters perform Unforgivable Curses left and right. As I understand, that's the whole point of word "Unforgivable," that if they truly did that, then it should be very hard to say "I am sorry, I didn't mean to".
It's just strange that a bunch of them were still around at Voldemort's rebirth.