Well... I still have a few episodes to go before I finished watching Season 5 of the Mentalist.
I know, the most obvious theory isn't always correct, but in this case... I have two suspects that I really like for this.
1. Bret Stiles
Lorelei said that Patrick and Red John were much alike, manipulative and playing mind games... When she escaped from prison and was in the Motel with Patrick Jane, she said a few things that totally reminded me of Stiles' cult: Visualize. She said after her sister was killed she "found her true self. Nothing can hurt me". That sounds much like Visualize.
And Bret Stile surely knows how to play with words and people's minds.
Although... I think he's somewhat too nice for that. I came to sort of like him in the end.
2. Bob Kirkland
Why? Well... He's high up, if I'm not mistaken. He could have the powerful friends that Red John has throughout Law Enforcement. He pushes the CBI off the Red John case, doesn't want anyone to talk to the only witness who could identify Red John, after Lorelei shot the man. (Sorry, I forgot his name).
And he was the one at the hospital, asking these weird questions, if he had ever seen him before and if the man would remember him. Why would Kirkland kill the only living suspect who can identify Red John, if he was chasing that serial killer? I believe he either IS Red John himself, or he at least is a close associate of Red John's.
These are just my main suspects, but I know the producers of the Mentalist do know how to keep their fans on their toes. And after all... Gale Bertram might be a possible suspect, too. After all, in the beginning of Season 4 (I think it was S 4) he quotes the second verse of William Blakes' "The Tyger" and states it's just an old poem he likes. So maybe he could be Red John too.... but he almost seems too nice for that....
