Was Bellatrix 'insane' before Azkaban? I'm trying to imagine Bellatrix prior to Azkaban, and I come up with two possibilities:
 
1. - that she was a colder, less jubilant sort of sadist prior to Azkaban, because her insanity doesn't factor into her malevolence.

or 2. - that she was always as gleeful a torturer and killer, and that Azkaban had basically no effect on her mentally.