After the last episode I got confirmation to a thought of mine. Red John isn't a single person. All the 7 people on the list are parts of the Red John persona. The last one(s) who'll stay alive by the end of season will be the brain(s). As we've seen Partridge cited from W.Blake. And the psychological description of RJ contained traits of all of the ones who were alive.

This seems to be getting very confusing, but after Jane walks in on the meeting with the 3 suspects, Jane leaves and then a comment is made:Agent Smith says to Bertram: Exactly how much does Jane know? Bertram responds saying: That is the question, Agent smith responds: Its your job to know the answer, Bertram responds saying that he is doing his best. My theory is Red John is not Just one person but a group of people, Red John is made up of all seven those suspects

Wow, watch 6x02 again and listen to what Bertram says to PJ at about 09:40: "if you have RJ in your sights, I will be there". He did not say "I want you to tell me" or "let me know immediately", he said "I will be there". Like he was RJ himself, hiding right before PJ eyes, telling him he will be there once PJ has finally discovered that RJ is him.

Am I the only one to think that whether someone is a good whistler is nothing a psychiatrist would care about? It is just not relevant at all for a psychological profile, is it?

Also, how did Sophie Miller know about the whistling abilities in the first place? A calm guy who "needs no distraction" while sitting in the waiting room surely did not whistle the charts (which would be a form of distraction).

I am pretty sure Bruno Heller wants to set us on the wrong track with this one.

Based on the info we learn from S6 Ep 2, I think RJ is not 1, but a number of different suspects together from the list that Jane has compiled. 

When you think about it, this would explain so much as to how he covers so much ground in such a short amount of time and keeps on the tracks of Jane and the CBI team so promptly - enough so as to stay one step ahead. 

I think the meeting between Bertram, Reede Smith and McAllister gave a really big hint in the latest episode as all 3 of them could be working together under the single banner of "Red John."

Unsure as to who is the lead in the operation, based on the small conversation conducted between Smith and Bertram soon after Jane interrupted their meeting at the CBI, I think they are all involved. Considering that Smith also freely brought up the topic of Jane and questioned "How much he knows?" to Bertram in front of McAllister, he would also have to be involved otherwise "RJ" would be releasing privileged information to an outsider. 

In this trio:
Bertram would be the CBI intel as he would have eyes on Jane, Lisbon and the rest of the CBI team round-the-clock.
Smith would be an inside-man from the FBI and he would provide more top-secret utilities towards the trio as he would be able to access government documents and track people secretly. This is best described when RJ found out about the tracking that Lisbon ordered Van Pelt to put on each of the 7 suspects - Smith would be the ideal candidate here. 
McAllister would be the rural addition to the trio as he can cover a lot of ground out in the rural areas where RJ is said to be a "local" - particularly evident in the cases with the "twin sisters" and "Roy Tagliafero".

Red John has been evident throughout the series in all of these scenarios and each of them make sense after you think about the finer details of the series. This theory also makes the series a lot more believable - considering that "many hands make light work."

I think it is setting up to be Bertram because he is so interested in the case and his voice could easily disguise as Red John and he would have been next Boss after the whole limo fiasco with Wainwright. Or it could be Ray because Red John didn't kill Lisbon because he "liked her" (Jane said) and Ray visited Lisbon in hospital and said "I like you Lisbon. You and me, we'll have our time." Or if Partridge really isn't dead, it could be him because he's creepy and all plus his voice sounds calm and weird like Red John. How else would he know to say "Tiger Tiger"? If Red John told him to tell Lisbon that, I don't think he would waste his dying moments on that. And what better way to hide your true identity than to make Jane think your real identity is already dead?

There really has only ever been three suspects for me bertram stiles and partridge they have been with us the longest. Macalister was only in one episode and the other are all recent add ons.  They have the most developed characters in the show and with patridge being dead(proving he is involved) I believe that points the finger at one of these two being behind it if not both