I don't have a theory that points the finger at any one character in particular but I would like to attempt to rule some suspects out.
I find it highly unlikely that Red John is in a high-profile, position of power within law enforcement. These characters are too recognizable and their movements are too easily tracked for them to be as effective of a killer as RJ. I believe the characters of Gale Bertram, Virgil Minelli, Osvaldo Ardiles, J.J. LaRoche and Judge Manchester can effectively be eliminated from the suspect pool by evidence gathered from the season 2 episode "His Red Right Hand" where Sam Bosco's secretary/killer, Rebecca is being led to her holding cell and is poisoned by a uniformed guard. The smile of acknowledgement on her face indicates that she indeed knew the man approaching her, leading me to conclude that it was likely RJ himself. Were any of the previously mentioned characters actually RJ, they would have most certainly been recognized by the guards escorting Rebecca. Although Red John has many contacts within law enforcement, I highly doubt the conspiracy goes so deep that several officers wouldn't question a high-ranking figure walking around in a guard's uniform.
Several people have offered Miranda Martins' murder by the fish hook as evidence that Virgil Minelli is RJ. This evidence is explained away by Jason Lennon's deep sea fishing hobby and the fact that he confessed to bringing Miranda to Red John. In my opinion, it is not solid evidence of Minelli's guilt.
The characters of Craig O'Laughlin, Luther Wainwright, Sam Bosco and Lorelei Martins can obviously be eliminated because they're dead.
I think there has been enough evidence presented to confidently state that Red John is indeed a man. Therefore, all the female suspects can effectively be eliminated.
The infamous "He is Mar" scene, from the season one episode "Red John's Friends" is probably the most significant and debated clue so far. I suggest that Jared Renfrew was not attempting to scrawl a name on the bathroom wall as he bled to death. If he were simply going to name Red John or one of his contacts why waste precious seconds writing "He is" instead of just naming a name? That's just a tad ridiculous. I believe it is liklier that Renfrew was attempting to write a description and not a name. I also think that this clue was intended to torture the audience and not actually be helpful.
Brett Partridge, the forensic analyst, fits the RJ description but is not Red John. I don't believe that he and Jane have ever shaken hands and Jane appears to strongly detest him. If Lorelei Martins truly wondered why Jane and Red John didn't become life-long friends when they shook hands then I don't feel that Partridge is a good candidate for Red John. There has never been any indication that Jane and Partridge would ever get along. The real Red John wouldn't be so obvious about enjoying the gorier points of a career in crime investigation.
Ellis Mars is not Red John. I have no evidence to back this up other than that he is an idiot and the hope that Rosalind Harker has higher standards than that.
Brett Stiles is not Red John. However, he indeed knows who Red John is and fears him which is why he hasn't outed Red John to Jane. I believe that Brett Stiles inducted RJ into Visualize and that he personally schooled him in leadership and manipulation techniques. I believe that Stiles feels enormous guilt for his part in creating the monster Red John has become and that is why he continues to co-operate with and help Jane rather than because Jane cleared him of murder. I believe that eventually Red John will kill Brett Stiles.
Robert Kirkland is not Red John. I believe that Kirkland has been introduced in order to inject another road block into Jane's investigation of the Red John murders. I believe his position is also too high profile to afford him the anonymity Red John requires. I think that Bertram and Kirkland believe that Jane is Red John and their exchange of "Can she be trusted/Who can we trust"?, with regards to Lisbon, is an expression of their concern that she and her team are aligned with Jane and may be unduly influenced by him.
Grace Van Pelt is a woman and cannot be Red John. However, I am worried about her absence. She has already shown that she is susceptible to Visualize's propaganda and I fear that once she returns, she will be primed to become a Red John follower.
Ray Haffener could possibly be Red John but I believe he is probably more of a red herring. I think it's possible that he knows Red John but does not realize it. He could become a potential victim of Red John if he discovers RJ's identity as I believe he would tell Lisbon if he indeed knew.
Red John is almost certainly another mentalist and is very closely connected with the Visualize organization. Nearly all of his associates are troubled individuals who would make ideal prey for someone as well versed in manipulation as Red John. I believe it is extremely likely that RJ is a former, possibly current performer with talents that may even exceed Jane's own. It is also likely that he is an exceptionally skilled hypnotist. While Lorelei Martins revealed that Red John and Jane have indeed met and shaken hands, it is never explicitly stated that this meeting occurred during the course of the series. While it may be possible that we have already seen Red John unmasked, it is not a proven fact.
There have been subtle clues left that make it possible for Red John to have been a carnival performer, like Jane, but those clues could just as likely be Red John telling Jane that he knows more about him than Jane perhaps thinks he does. Others have suggested that RJ could be Jane's brother-in-law, Danny or even his own father but I find these scenarios highly unlikely. Red John only began targeting Jane after the talk show incident and if RJ were indeed a family member, Jane would have been targeted long before that. Also, Danny blames Jane for eloping with his sister and for the eventual deaths of her and Charlotte. I would think that if Danny were their killer, his attitude would reflect more mocking. I believe that it has been mentioned that Jane's father is dead but if I am wrong about that I still don't feel that the father is RJ. Who shakes hands and becomes life-long friends with their own father?
If we have indeed already met Red John, my bet is that it has been brief and extremely ambiguous. We were not meant to be drawn in by the moment so that when Red John is finally revealed, we will all be in shock and gasp, NO WAY!
