Correct me if I'm wrong, but if Portius wasn't the actual mafia member carrying out the kill, wouldn't my jailing him do absolutely nothing? If so, he's still on the suspicious list.
I'm going in blind here due to not having any knowledge of the characters, so I've tried to be mostly silent. I'm also inclined to believe Sidd is town; he tends to bluster more when he's mafia, and his daykill isn't really mafia-esque imo.