it is basically clear that red John is Bret Stiles. and his acomplicce is Brett  Partdrigde. is it a coincidence that they both have the same name?

in episode 8 season 5, lorelei confirms to patrick that he has already met Red John, and that it is a wonder how they didnt become friends when they FIRST SHOOK HANDS. so patrick has met him. as to partdrigde, he is clearly someone important, like some sort of mole that stiles might have in the CBI. We already know Red John is powerful, so thats another insight for stiles, that claims tohave friends around the state. how did Bret Stiles managed to get Lorelei Martins out of prision. ¿ has he already met her? how come it becomes a homeland security matter? this are all questions that will lead us to red John.

Robert Kirkland is the alleged serial killer Red John. On season 5, episode 5, a woman named Alexa Schultz calls the director at the time (Virgil Minelli) and requests that he gives updates on the RJ case. She told Minelli she works for the FBI an that her boss would appreciate what's going on in the case. Minelli agrees, and has no idea that RJ was in the same car as Alexa. They revealed Robert Kirkland as Red John and the scene ends. (He also works in the FBI.)

It might be Patrick's father Alex.
He hasn't been on the screen that much, but he had some appearances.
Red John is good at manipulating people. Alex Jane used to be a psychic, together with Jane. And 'Tiger, tiger' might have been a poem he used to tell Patrick when he was young. 
I can't think of a motive for being Red John, but he might have been angry with Patrick for something that has happened.

My view is that RJ serial killer does not exist.I think PJ's wife took her own life after first killing the child. This would explain what Kristina Frye told PJ about his daughter not suffering. Her mother would have taken care not to hurt her. The note that PJ found on the door was a suicide note. The deaths caused him to have a breakdown and he created the Red John persona in his mind to take the blame for what happened as his wife was obviously ill and he didn't see it. He is now trying to find redemption by using his talents to help the police. Every time we see a smiley face (resembles P.J.'s face), it corresponds not to an RJ murder but to a death for which PJ somehow feels indirectly (if not directly) responsible/guilty. Eg. Jared Renfrew could have been murdered by anybody but would still be alive if PJ had not had him released from jail. Rosalind Harker is not dead but the smiley face represents PJ's guilt as he treated women the way Rosalind was treated. He didn't manage to use his skills to read Rebecca who obviously worked in the building with them and prevent Bosco's murder, so feels guilty. Same thing for murders committed before his family's death. PJ. feels in some way responsible. PJ. killed Panzer to stop him killing again and prefers to deal with it in his head by blaming RJ. Now his dark side/RJ persona is starting to take over his life. The more things go wrong, the more he blames RJ. The Tiger Tiger poem represents the struggle between his light and dark sides. Which side will win out in the end? This theory does not obviously explain everything but would explain certain holes in the procedure as certain things are happening in PJ's head and not in reality.