So red john is the tyger, patrick jane is the lamb. Similar qualities, different morales. They come from the same creator according to William Blake, cited English poet. Same mother, same mentor?

It couldn't be anyone other than Haffner. I'll explain, the bold parts are my reasoning why i feel it's relevant/why i think he's RJ. Normal text covers the facts.

Let's begin with his career background. We know he was part of an FBI unit that dealt with surveillance, until he transferred to CBI, where he was briefly agent in charge (a male Lisbon). This is relevant considering 6:01, which dealt with wiretaps on the RJ suspects. As an expert in surveillance, he would have known that his phone was being monitored,  and he would be skilled enough to manipulate the situation to his own needs. 

Whilst team leader, he was manipulated by Jane, yet was aware of it (others aren't so sharp), whilst at the same time manipulating Cho into working for him. Jane still prevails and makes him look foolish. He could have easily played the fool, the fact he was aware he was being played shows intelligence that others haven't displayed. By allowing Jane to play him, he played Jane, by hiding in front of Jane's very eyes.  His manipulating of Cho showed a darker side, and a ruthless streak. 

He leaves CBI to form his own independant company (that is bankrolled by Visualize). He tries to recruit Lisbon. His attempts to recruit Lisbon show that he understands what is important to Jane, he was probably just gauging Lisbon's feelings towards Jane, thinking a few moves ahead, how he could try and drive a wedge between Lisbon and Jane professionally. 

He is a member of Visualize. RJ is a visualize member, it's the only way Bret Stiles could know so much about him. 

He was at the Farm in 1988. He didn't expect to get found out here. He looks shocked when Lisbon reveals that she knows. He tried to palm blame for the 3 murders onto the girl, when she was only guilty of 1 count of manslaughter. 

He shook hands with Jane. Self explanatory.

He played college football, likely for Alabama Crimson Tide Crimson = red. 

He is around 6ft tall, medium build, with short/medium hair. He perfectly fits Rosalind Harker's physical description of Roy Tagliaferro

He is one of the remaining 6 Of the remaining 6, only he and Robert Kirkland really match the description, but why would Kirkland break into Jane's room for RJ info if he was RJ, which again leaves the finger pointing at Haffner.

He had discipline problems as a youth One of them likely being anger issues, leading to murderous impulses.

                                                            Red John

                         
                                                               Facts


1.      Was a teenager/young man in 1988.


2.      Described as being “Just under six
feet, with short and straight hair, not muscular but not soft, strong hands”.


3.      Has extensive knowledge of computers
and monitoring devices.


4.      Believed to be a member or ex-member
of “Visualize”.


5.      Shook Jane’s hand and is similar to
Jane.

                                       
                                                       Ex-Suspects


1.      Brett Partridge: Never shook Jane’s
hand.


2.      Robert “Bob” Kirkland: Had no reason
to break into Jane’s apartment; Red John already knew everything.


3.      Bret Stiles: Too old; wasn’t young in
1988.


4.      Gale Bertram: Doesn’t match the
description given by Rosalind Harker.


5.      Sheriff Thomas McAllister: Wasn’t
aware of who Jane was when they met and is slightly too old.


6.      Reede Smith: Too heavyset and seems
to lack a lot of intelligence. Has a partner in the FBI, making it difficult to
conceal such a large secret. Possibly a Red John associate.

                                                          That Leaves…


1.      Ray Haffner. He has the experience
with technology, is a Visualize member, fits the physical description, and has
been in the FBI, giving him contacts.                             

To begin with, this intro is not a theory as such, but I've read elsewhere that the famous Red John voice is actually done by Simon Baker, not whoever plays the character that will be revealed as RJ. Plus there is that YouTube video doing the comparison in voices, and unless it's a perfect imitation, it's definitely Simon Baker's voice in the limo (season 4 finale). The season 2 ending sounds like it could be done by Baker too, he is pretty good with voices (i didn't realise he was Australian until i saw the DVD bonus features of Season 1).

Will be interesting when RJ is revealed if the actor can actually do the voice, or if they have to dub Baker's voice over when the person reveals their dark alter-ego. 

One final thing, my guess is Haffner. The tracker location in 6:01 stated that he was "In Transit", and a car did pass Lisbon as she was entering the house, maybe it was a disciple with Haffner's phone in the car to distract attention? Add that to the visualize angle, the physical description, the numerous throwaway clues (Red Barn).

So I have no idea who might be RJ, but there are a lot of people who think that Brett Partridge is RJ. And this is why I'm not sure about that: 

If Partridge pretended to be dead it would be to keep Lisbon alive so that she would think he was dead, right? BUT I think in that case Lisbon may remember someone grabbing her from her feet! And that could only be him! So she would know Partridge was not dead, so that may work against him. That's why I have concerns about this theory.

Besides, I think that if there's no body, Patrick wouldn't be fool enough to think Partridge (being one of the suspects) is dead. 

On that big clue Heller talked about, something about the sink Lisbon stares at makes me wonder. As I read somewhere before, I don't think it is possible that the door would just open without any help. I think someone was there. And also the car when she's out of the house, that was suspicious. I don't think anything they put in the show is a coincidence, so all of that has to be there because of a reason.  

My theory is that red john is ray haffner. I dont think red john works alone, he has at least one accomplice in the list of 7 (or now 6), but red john himself is haffner and here is why i think so.

He meets the physical description given by rosalind ( he is slightly over 6 feet and i know rosalind said red john was just under 6 feet but how could a blind woman know the exact height of a person?. So red john is 6 feet, give or take.

His age also makes him old enough to be red john. He is old enough to have been at the red barn in the visualize farm in 1988 (this will be important later).

Talking about visualize, he is a member of the cult, which would explain some of red johns contacts, specially bret stiles. Because bret stiles seems to know a lot about red john meaning that red john would very well be a member of visualize and stiles has to protect and help him. Him being a member of visualize would also link him to the red barn in 1988 because that was a visualize farm.

And lets remember his statements to lisbon. He said that as a teen he was troubled but then visualize took him in and helped him. Him being troubled as a teen could mean that he is really a psycopath and killed those people in the barn back in 1988 and went to visualize for help or something along those lines. Or visualize covering up for his murders since he was a member.

Lets not forget that when lisbon says he suspects him of being in the barn in 1988 he just shrugs it off and walks away. To protect visualize or to protect himself??.

Getting on to his job, he formerly worked with the FBI which would explain red johns high ranking contacts, ( Robert Kirkland maybe?, i most surely think he is an accomplice of red john, he works for homeland security after all, and had a friend in the FBI Alexa Schultz).

He also worked in the CBI which would explain red johns contacts in the CBI and tie him to bertram, who i think could be another accomplice of RJ. It would also explain how red john was able to be ahead of jane always and kill that woman inside the CBI building who was going to confess about RJ.

He used to work in the FBI in the organized crime division, and is an expert in wiretraps and surveillance techniques (according to the mentalist wikia). This would explain so many things as how red john knows so much and is ahead of every move the cbi team make. Or how he is impossible to catch. This could also explain why he knew lisbon had hacked the phones and therefore set her up with partridge.

To end this, his relationship with lisbon. He now works as a private detective (gives him more freedom to act i guess) and offers lisbon the job beside him, with a pay raise etc. I noticed he gets very angry when she refuses, because she says she cant leave jane. He seems like jealous that lisbon prefers jane over him. Yes, i think haffner aka red john has some feelings for lisbon and thats why he hasnt killed her yet, he has only captured her. He wants jane to act now.

First of all, I'm uploading an important image below in the comments, showing a comparison between the back shots of Rebecca's killer and Haffner. And also proposing a theory as to how RJ got the info on Aileen and her connection with Jane's memories and also the whole Loreli, RJ's List ordeal.

For most of the time Bertram has been at the top my list and so has Haffner. Since they both can be Red John I'm going to explain why the either can be RJ.

Haffner

1. Fit's Rosalind's description quite well except for the voice (although RJ has to be faking that pitchy voice, he wouldn't make such a silly mistake).

2. The visualize connection, and they "screwed-up kid" remark and the whole thing in The Red Barn episode where he tries to manipulate Lisbon.

3. He is an ex FBI Agent (that explains RJ's connections in the FBI) and ex CBI agent who specializes in Creative surveillance techniques. Which means he has the skills and resources and the intelligence to hack the CBI Network (while attacking Bosco's team or when Jared Renfrew escaped or when He followed Darcy and in this episode as well.

4. The handshake and more importantly his demeanor during his first appearance. He seemed a little friendly towards Jane, no? As if he really admires him on some level and was glad to be finally able to get a chance to spend time with Jane. And the through out the episode where he show's his manipulative and inquisitive side.

5. Consider looking up the personality traits of a psychopath and compare these guys with that. Both Haffner and Bertram do seem to have some of the traits. (Of course Jane has been diagnosed in the show as a clinical psychopath, but I think we can exclude Jane and just spare him of that accusation :) )

Bertram

1. Did shake hands with Jane, and called him "Boy wonder" as he was called in his early days.

2. His involvement in the RJ related cases such as the Todd johnson murder, Hightower frame-up and Loreli Martins.

3. Just like Haffner, Bertram too behaved in a friendly way with Jane initially and did say that he admired Jane's skills.

4. He's the opposite of Rosalind's description. Now think about this - RJ has killed everyone who can identify him except Rosalind (and the little girl Haley too). So why not Rosalind? She already gave his description way back in season 1? He must keep her alive because she hasn't broken his trust by giving the CBI the wrong description! She said Roy is just under 6 ft tall, Bertram is the opp - as tall as 6.2 or 6.3. Has short straight hair and Bertram - BALD :P. Not muscular but still strong (Well he is that) and the voice - which as I explained above, is fake.

5. I read a theory on this site somewhere that the "He is MAR..." message could actually be Renfrew writing "BERTRAM" in REVERSE, which would have been MARTREB. I really liked this and this supports my theory well. Cudos to whoever wrote this theory! :) 

6, In the latest episode, Bertram says he know's about Jane getting closer. But At that time, only Teresa, Patrick and RJ knew that Patrick got closer. Cho and the guys didn't even know! And the way he talks to them and the line where he says i am many things to many people, doesn't that remind you of what Timothy carter said after BERTRAM left him and Jane alone at the mall?!

Now finally, a theory about how RJ could have come up with the list just like Jane's and also know about Aileen

Either Bertram or Haffner, could have kidnapped or somehow in the past have been in contact with and gotten the info about Aileen from people who could know about Jane's childhood. And there are 3 people who could possibly know that - Alex Jane, Sean Barlow and Dr.Sophie Miller (if I got her name correct).

Now we've all seen the way Bertram approved Kirkland access to the RJ investigations. This almost seems like him cleaning up his mess and not getting his hands dirty. Which also means the the mysterious Mr.Kirkland is actually an associate of RJ. That explains why he asked Lennon if he knew him and not RJ and still killed him and said that thing about having a friend who would do this for him. IT just means he's doing the dirty, risky work for RJ.

And about the list, I'm sure that Patrick has a different list and RJ has a different one. And that's because Jane suspected a break-in and that's what happened. And as we know who broke in we can say that the real RJ, either Bertram or Haffner has been given the wrong info by their associate Kirkland.

I hope my theories have interested you and if you have and complaints/suggestions/criticisms/corrections, please let me know! :)

And don't forget to check out the picture I'm uploading below in the comments!!