How do I arrest the King's killer, Rodrigo? When I arrived in Alvaron one of the first things I did was examine the body of the King and talk ot that man, and now I got the quest from Christoffer, but I cannot arrest him? Am I missing something?

EDIT: I'm sorry, I just noticed my savefile glitched up and I hadn't gotten the quest from Christoffer yet, I think this will solve it -_-

Edit 2: Actually no, I still can't arrange his arrest!

I'm not that far into the game yet, but according to the script you need:
- the testimony of the chamberlain Trisstan,
- the testimony of Cardinal Letti,
- to notice Rodrigo's injury.