I think it was luther. 3 main reasons. One, Patrick and Luther shook hands on the episode he was first introduced. Second, He fits every single description of red jhon. And three, in season4 episode 24 was that not him in the back of the car? I don't know for sure, I only watched that little clip. Oh and  I LOVE JISBON AND RIGSPELT. Sarah went and ruined everything. And too bad Chummer didn't turn out. :'( Anyways, my vote is toward Luther.