A few suspects that are going through my head right now.
Our first suspect is Bob Kirkland. When he made his first appearance Jane says, "Do I know you?" and Bob replied, "No. But I know you." I got a little intrigued but at the same time creeped out. Also, the fact that Kirkland is so interested in the Red John case as a Homeland Security Agent is a little like the Panzer episodes, (meaning he is investigating himself). Though he isn't one of the more significant characters in the show, there's a decent chance he is RJ.
Bret Stiles... the Visualize psycho. He himself stated to Jane that Red John is "someone he knows". But how would he know that? Is he Red John himself? It is possible he is Red John and his Visualize zombie minions train to become one of his accomplices? Suspicious... but in my opinion he isn't the sort of person to be Red John.
The thing about Brett Partridge is that he himself doesn't nearly have enough significant characteristics to be Red John, though I do believe he is one of his assistants. What made me conclude this is because of his behavior around Red John's crime scenes. He seems somewhat anxious, and hateful towards Jane, not something Red John would do. There is also a scene where one of RJ's apprentices attack a victim and at first glance, it appears to be Brett doing to deed.
It's possible Gale Bertram is RJ, but there isn't much evidence against Mr. Bertram. The only feasible clues I found on Bertram was when he said the "Tyger Tyger" poem, which was pretty shady seeing as it's not very well known. Also, there's something about Bertram that reminds me of Red John... the power he has, his ability to "cold read". It's almost like you secretly know it's him.
J.J. LaRoche was definitely a more primary suspect in earlier seasons then he is now. But I still believe there is a possibility LaRoche is the culprit. There was a lot of evidence pointing towards LaRoche earlier on, but now there is only one hint (to my knowledge) of LaRoche's being/involvement of/with Red John. The episode with the supermarket bomb guy that turned out to work for Red John was shot by LaRoche because "he reached for a gun" before being taken for questioning down at the CBI HQ. Because of this it is possible LaRoche is one of Red John's helpers or Red John himself.
Now this is who I believe Red John is himself: Patrick Jane! It sounds pretty crazy, but after watching a ton of episodes the pieces somewhat fit together. I just find it so strange how he, like Panzer, compliments Red John's killings, one time saying "he likes to cut their throats slowly and watch the life drain out of their eyes" (or something like that). I'm just wondering how Jane knows all this stuff? About his family, it's quite possible there was maybe a falling out, and before he left for the interview he murdered his family, releasing his monster within, the birth of Red John. There's a lot of episodes where he talks about RJ in an admirable fashion, yet he talks about killing him a lot. It's possible he has gone crazy after murdering (?) his family and believing RJ is out there though it is him. We'll just have to wait and see...
Well, that's my overall opinion! The reason I didn't list Ray Haffner, Reede Smith, or Thomas McAllister is because I don't believe they are Red John. Feel free to share your thoughts on my theories!
