Ugh... the flags are very complicated...There are more or less two ways to get him(100% guilty, not partially), one if a lot of people lived (because a lot of people living balances that the Trial was not really that hard) and one if a small portion lived(more believable).
There are some depoiments that harm your case and some that helps. Basically, don't speak with Doller, Landen or Khalmac.
Also, if you helped Malev get into the Master's quartes, it ALSO lower your chances.
If you had sex with Rosa, she will not fuck up your chances... otherwise... best to keep away from her. : P
Also, if you did have sex with her, Diana will snap her instructions. It's best to give it back if you have a lot of apprentices alive, aside from that, it's better to keep them.
That's all I can say from the top of my head though... : P