This is not a theory.
I am a little mad because if i was writer of this awesome story i would plan ahead.
I would decide who RJ is before the first episode airs, I would decide how they will discover him and capture him and i would think about the first episode in which i would put him. I have a feeling that the writers changed their minds on who RJ is many times throughout the series. If you write this awesome series you better plan everything about the main story. I would develop RJs character more, he would have at least 5 appearances throughout the series. I would develop other characters ,like RJs suspects, more so they become suspicious to the viewers.I mean i will be satisfied with RJ only if he is brett partridge or if he is Walter Mashburn because they show up early in the series and they seem like sociopaths and they both seem like they have something dark around them. But then again they werent developed enough walter mashburn appeard only twice.I only wish that writers planned ahead and decided who RJ is straight away and that they developed him some more and other suspects too.

What a huge let down.
Firstly from having so many absorbing and engaging characters too choose from they decide upon some of the most boring and humdrum characters to be on the final 7 list to be Red John.
Secondly this Tyger Tyger coalition is a load of drivel and total absurdity.
Thirdly Bob Kirklands pursuit of Red John is thoughtless and irrational, murdering Red Johns disciple in hospital without interrogation is unreasonable and then at the end of the previous episode for him to smile and accept his fate as he is commanded to run away and get shotdown by 6 bullets is mind boggling. That as too be the most flimsiest attempt of revenge I've ever seen.
The first episode of season 6 was brilliant, the last 3 have been dense, mediocre and inadequate.
We still have no concept of the He is Mar that was supposed to be revealed in the previous episode.
This show as gone considerably way off track.
Sadly disappointed.

No scenes like Rigsby and Cho scenes :)

Ok, I read some comments posted under some theories.....and I agree.....An unarmed and chained "Prisoner" is always tazed, and never shot.....even if they shoot, its just one bullet in the leg or hip....not in the back and that too to kill.....FUCK NO!!I can tolerate BS, but this is ABSURD!! Beyond BS!!!!we love your show Bruno, please do not think of us as stupid !!!Even if it was Michael Kirkland that was shot, it was not the right way to do it.....HELL NO!!!And for all our international fans posting their theories.....It is a BIG deal when federal employee is killed......someone definitely calls the hotline or leaks it to the press.....there is ALWAYS and I repeat ALWAYS a whistle blower / vigilante.....so please, NO MORE NONSENSE Bruno!! 

I don't think anyone on Jane's "suspect list" is red john.  I think red john is Bob Kirkland's twin brother.  Bob Kirkland told of how they both grew up with an abusive father who physically and mentally abuse them and their mother.  He told of how their mother committed suicide with a razor blade.  His twin brother seem to be the only one we know of, who is damaged enough to be a serial killer.  I think he met Bret Stiles and he joined visualize which helped him kick his alcohol addiction and gave him an amoral code of inner strength.  Bret Stile pointed Jane to the house Red John was holding his "psychic" friend.  I think Jane met him very briefly and he was in disguise. 

(please excuse my english) Ok, first of all i'd like to say that this is my favorite show,and bruno heller is a genuis. but i think it got a little overwhelming for him to make red john cases as interesting as it used to be,because now he has to follow all the clues from 5 seasons .
as someone mentioned previously, i don't think it's a coincidence that suspects that are being elimanted from the show are the ones who had the most votes on this site, which means they keep track of this site.. 
and now they've turned it into a conspiracy show like prison break did with their last season ( "the company and scylla") ;which was fine for their show, but it doesn't fit for the mentalist.. 
I always imagined red john being just a one person, not that there is a company of some sorts, and now i think it's just unreal that patcik jane can take down a whole company. 
And if red john is a one person, i just don't think it is anybody from that list, it just doesn't fell right, and there is something strange about it, nobody from that list has that "look" that i imagined red john would have.. i know bruno said we can trust the list, but i still don't ....
The list suspends the suprise when we find out who is red john because we're already prepared for each scenario for the suspects,and that's why i think the list was a bad idea... 

I believe Heller was reading our theories and when we guess something right, he was voting unlikely to make us think otherwise. Eventually it didn't work and he changed the story.

My guess for RJ is Charlie Sheen. The guy has tiger blood.