I wont pretend to know who Red John is, I'm just throwing a few ideas out there. Ray Haffner doesn't immediately stand out as a suspect, due to the lack of emphasis on the character in his episodes. But I think it could potentially make sense.

So we know RJ was involved with Visualize, I believe he is a member, but not someone who is high ranking. I first had my suspicions when Bret Stiles started telling Jane about how much he knows about Red John. Bret Stiles is very rich, but the only influence he has is in Visualize where he knows almost everything about his members. 

When Christina Fry was kidnapped by RJ, Stiles met up with Jane and gave him Christina's location. Calling it "a gift from a friend". Red John must realise that Stiles was leaking information, as if I remember, the house was in a pretty random location that only people who were told would know about. So why didn't Red John kill Bret Stiles? Anyone who knows anything about Red John is always killed by the man himself. Two explanations:

-Bret Stiles is Red John
-Red John is a member of Visualize. And as we know, no member of Visualize could harm Stiles.

I personally don't think it's Stiles, even though he would be a fitting Red John. I think it's more likely a low ranking member such as Haffner. 

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I also have a semi-theory relating to how RJ knew about Jane's happy memory. If we can all accept that PJ is not RJ himself (PJ's several encounters with him, why didn't Lorelei just shoot Jane if she knows he is RJ? Plus Heller telling us very non discretely that "Patrick Jane is not Red John" in a recent interview about the list.) then we must turn to the eerie world of HYPNOTISM.

Any of you who watch any of Derren Brown's programmes may be aware of snap induction. It's a form of hypnotism where you can put someone in a trance by shaking their hand. 

But would Jane "fall" for that, being a Mentalist himself? So many questions. Once you answer one another appears. I just know that I can't wait for the next season.

Thanks for reading and enjoy the show :)

Ray Haffner is Red John.  Stiles, Partridge, Kirkland and Bertram are too obvious. Too many clues for these cats have been left to throw us off.  Smith and McAllister could be Red John because they have no history and a storyline could be established around one of them next season.  

I have many reasons including my great HATE of Haffner however I will just stick with the main 3.  Haffner states he joined Visualize because he was a troubled 17 year old going down the wrong path.  He has a football trophy in his office and several people online have hinted that he has a football background.  If he troubled enough to join a cult, would he actually be involved in playing a team sport such as football.  I am guessing the 17 years olds that Visualize are recruiting do not have a positive item in their life like football can be.  If my time estimation is correct during Haffners college age he would have been on the farm and not on campus playing ball.

I also believe Haffner has the physical goods to carry out the murders.  Red John kills at will and it doesnt seem like there is much fighting back.  Red John strikes swiftly and powerfully it seems.  Haffner fits that physical bill.

Haffner is a manipulator and liar in a very subtle way....behind closed doors with Cho......his attempt and getting Lisbon out of the CBI.......I am also guessing that all of Hafnners credentials are fake.  I also think that Haffner has gotten involved romantically with Lisbon and this will come out in the next season.  I think his invitation to Lisbon was to get her away from the CBI and hopefully have Jane working for someone less tolerant of his actions and thus getting Jane off his trail.  I also think that Haffner wanted to hook up with Lisbon to get closer to someone who knows Jane.  JAne is getting closer and Haffner knows it.

Haffner is a sleazy douchebag.  Just look at his eyes.  I hope Jane kills Haffner.  I HATE HAFFNER!

Ray Haffner is Red John!!!  Ray Haffner is a sleazy douchebag.  I cannot wait until he is brought to justice.  I HATE RAY HAFFNER!

After I've shown you my theory about Partridge, I want to show us also that one about Raymond Haffner.

Haffner strongly returns to be a candidate as possible Red John.
Telling the truth, I wouldn’t like this choice, but everything’s possible.
Let’s see the reasons that allow us to suspect him. We ‘ve seen him just in two episodes, but we can collect a lot of clues.
He started his career in the FBI Organized Crime Division. Two important arrests using wiretaps and creative
surveillance technique. This could explains his contacts in the FBI and also the way he could get all the informations that he needs.

One of his colleague, the smallish Tork, dealing with Patrick says him ”I heard you used to be in the circus.” Maybe Haffner told Tork about that.

The case his team has worked on (4x02) involved a gym. Haffner declares to know that gym very well and that a lot of bigwigs work out there… so he has important contacts too.

In his office there is a football trophy, so he’s an ex player: just like Todd Johnson and FBI agent Craig O'laughlin. Craig, particulary, knew Amos Van Pelt, Grace’s father. On the episode 4x12 Van Pelt hallucinates and she sees Craig.
He tells her that he’s just a figment of her imagination and that she has to open her eyes all the way, if she want to see the truth of things. Maybe he’s speaking about football: maybe Haffner knew Amos Van Pelt too and he has become friends with O’laughlin, somehow.
Amos Van Pelt was the coach at Burton. O’laughlin has been a professional player (NFL) for a couple of years in Tennessee.

Haffner asks Cho if he thinks Patrick is smarter than him. Then he offers to be a spy for him in return for the job.

Haffner understands immediately that it's Patrick behind the heels trick against Tork.

Shortly after Lisbon made a call to LaRoche about Sally Carter, we can see Van Pelt trying to talk to Haffner, who says he's busy; he looks pretty thoughtful while pouring some tea.
By the way, it seems he is looking for Ron, considering the line of his sight. In that case, Ron could be one of his followers and this could explain all the clues we have collected against him as possible Red John.
Shortly after Sally Carter is found dead, apparently committed suicide, leaving a farewell letter.

Then, coming back to the case, Haffner finds the address book and says to Patrick that he checks on him: “Did you really think that was gonna happen? Like I wasn't watching you every minute?" That's a little creepy.

At the end, Bertram blames Haffner for have been kidded by Patrick and he dismiss him from the assignment. Haffner appears surprised, like he has really fallen in Patrick’s trap. But if Haffner is Red John, then this will be just a big act to looks less clever than he really is.

On the other episode, 5x13, authors try blatantly to make him more suspicious.
But let’s proceed step by step:
first he felicitates Lisbon and he’s sarcastic remembering the work experience with Patrick.
Then he invites Lisbon to have a lunch with him.
During this lunch he starts complimenting Lisbon for keeping under control Patrick at best, whereas he considers Patrick uncontrollable.
He also adds to know a couple thousand people who whould think the same thing.
Then he tries to persuade her to work with him, leaving the CBI and, particulary, Jane.
Later a weird fact happens: Ray nominates Jason Cooper and Lisbon realizes he has being a Visualize’s member since he was young; he says he was a screwed-up kid.
Later we’ll discover that Red John too has been a Visualize’s member in 1988 and that he has worked in a farm. If Hafner was Red John, I think he wouldn’t leave such a evident clue so easly. What for?
Maybe the authors gave us this information to mislead us and to make him more suspicious. But… never say never!
And when Lisbon asks him if he has been in that farm in 1988 his answer is even more suspicious: instead of answering simply “NO”, as anyone who has a spotless conscience would answer, Ray evades the question, answering her “Lisbon, we're still friends, right? Why would you ask me that?”
Maybe he has known Red John and he wants to protect him cause he has become an accomplice. But, one more time, he could be Red John himself.
But we have already learned that when the clues are shown to us so manifestly, they’re probably false… but who knows??
Anyway, the doubts against Haffner are significant. He’s not on the first place among the suspects, but he could be surely on the podium.
My Podium is:
Partridge;
Bertram;
Haffner.
Only missing Bertram's theory; I have one, but it's in Italian. Coming soon... :D
And there is also a theory about McAllister: I found something interesting, but I still think he was a red herring. Anyway, probably I will post something about him too.

Did anyone else notice what appears to be a marksmanship trophy in Ray Haffners office ? It did not go unnoticed by me. Red John displayed expert level shooting skills. RAY HAFFNER SUCKS! He is a murderous thug. I HATE RAY HAFFNER!

I want to follow up on my other posting that Haffner is Red John.  I cant stand this fool.  He is such a sneaky slime bag.  He was just faking being fooled by Jane.  He just sat there all smug during his lecture from Bertram, probably laughing inside at the scam he was pulling.  I also think Haffner is banging Lisbon.  I mean how many times has she gotten laid in 5 seasons?  Once?  He created this whole story about her having great investigative prowess and putting that to use in his PI firm.  The only reason Lisbon solves any cases is because of Jane.  F'ng Haffner is so sleazy.  Not that we all havent conned women into bed but Haffner is just a dirtball.  My hate for his character grows by the minute.  I hate the network for making me wait until Sept. to finally see what I already know.  I am guessing Haffner(REd John) will start to kill off the other members of Janes list one by one.  Haffner obviously has the physical goods to kill at will un-challenged. The bad news is I will have to spend several months waiting for Haffner to be jailed or killed.  I am guessing he will just escape and leave the country.  I FUCKING HATE HAFFNER!

Its Haffner.  No doubt in my mind.  He is very shady.  His timelines from back in the day don't check out.  He was a troubled 17 year old yet he has some fancy looking football trophy in his office.  When did he get this?  When he was a troubled 17 year old going down the wrong path?  When he was in college?  That would be right around the time he was out on the farm with those hippies.  I am guessing all his credentials are fake.  How about when he asked Cho who was smarter??  Haffner or Jane?  Red John has to feel that he is smarter than Jane and it probably is driving him nuts that others think Jane may be smarter.  This is probably why he vowed to start killing again often,  He wants to prove he can outwit Jane.  Look at Haffners eyes.  He has the look of a sneaky nutcase.  As a matter of fact, F Haffner.  I hope Jane kills him!  I HATE HAFFNER!