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.

i think that red john is luther wainwright is still alive his death was faked.The description of Rosalid Harker matches with him and his name wainwright is same Roy Tagliafero search in google about wainwright.Will be a big surpise.Iam sorry for my English it is not my mother language.

I suspect Luther. Limusine scene:
The bait has worked and Red John was indeed in the backseat. He is Luther. The death was fake.

i think he is in the top 3 of all the suspects