I've always had an easy time guessing "Who done it" and this is because I think about why the writers wrote the episode in a specific way, not why some random character would have motive or the means to kill another character.  For example since Patrick Jane is the one who catches the criminal in every episode, I always compile my list of suspects by "what character is introduced while Patrick Jane is around." This tactic of thinking about the episodes in a writer's perspective has made it easier to solve the series weekly murders due to the fact that EVERY action and EVERY line has to be put into the script before it can be seen on camera.

This is why I believe Brett Partridge is definitely Red John. Why do I believe this? because of other theories and because of the way the first episode of season 6 is written. I mean why kill off Brett Partridge unless you are trying to divert our attention else where? Also why would they give Brett Partridge a very nervous demeanor unless he has a reason to be nervous, I mean if the writers are planning on killing him off in that episode what purpose would it serve to write him in a nervous way?

Also in episode 5 Robert Kirkland says that he believes there is a secret organization working withing the federal government on major cover ups that Red John might be apart of (we all know he is, I mean "Tyger, Tyger"). Why would the writers add that "cover up" bit unless they are trying to subtly set up for Brett Partridge not actually being dead?

Also Brett Partridge is the ONLY suspect (of the seven) that was introduced in the very first episode of the series. I mean, if I were to write a series similar to that of The Mentalist I would most definitely write the killer Patrick Jane is after into the very first episode, NOT as a main character of course, but definitely as a reoccurring character so that you wouldn't forget him.

Now back to the nervous thing... In the 1st episode of season 1 Brett Partridge speaks and acts in a way as to say "I'm the specialist when it comes to Red John" but as the series goes on Brett's character seems to become more and more afraid of Patrick Jane which doesn't make any sense unless he knows Jane is getting close! Watch http://www.youtube.com/watch?v=hVmQFzq8Jeo and http://www.youtube.com/watch?v=DvG7i-U2C4A to see what I mean...

In episode 1 season 1 Patrick Jane says that Red John thinks of himself as a showman or an Artist, and in that very same episode Brett speaks of Red John saying things like "Trusty stun gun" "his sweet time" "pretty strong" "classic smiley face" as though he admires him.

Why is it that Lisbon finds Brett dead at some random abandoned house? I mean that makes 0 sense, why wouldn't the writers write him at his own house?  Also if Partridge isn't Red John than why is it that Lisbon falls in a way that would suggest that someone grabbed and pulled her feet our from under her that just screams to me "Partridge knocked Lisbon down" http://www.youtube.com/watch?v=w4mhDdZPD-o

Something interesting to me about Jane is that he calls Brett a "Ghul" which by definition is "a person morbidly interested in death or disaster."

And finally why have Brett say "Tyger, Tyger" unless they plan on addressing it more than having Jane say "That's interesting" I mean you wouldn't have a suspect say something that HUGE unless they were planning on covering it.

Most of this could be answered by the writers having Jane say something like "Brett was a Red John follower and did something stupid so Red John killed him" but I'd rather them not do that mostly because if I'm right and Partridge is Red John then I'd feel very satisfied with the way it was dealt, but if ANYONE else is Red John it just wouldn't make sense to me...

The reasons I don't think the other suspects are Red John...

Ray Haffner isn't because the writers have been making it WAY too obvious with the past couple of episodes.
We saw Bob Kirkland killed (unlike Partridge who we HEARD was dead).
Gale Bertram can't be Red John because Thomas McAllister said, "it's your job to know" (if Jane knows anything that is) I just don't feel like Red John would have to be told what his job is by a member of his own organization.
Brett Stiles is too old and wouldn't need to kill someone is the way that Red John does.
Sheriff Mcallister isn't afraid of heights plus he is just to little of a character to be Red John also there is NOTHING about him that suggests to me that he is.
Reede Smith said "There is an organization, and they even let little people like me in" as in "I'm just a puppet"... but idk I might be wrong, I mean his smile looks a lot like the Red John Smiley face.

The only other characters that would make sense to me to be Red John are

Van Pelt... Yes, I know she's a girl but what if that has been something Red John has had over Jane all along. Plus in the very first episode they introduce Van Pelt as a new member of the team, I mean why not just introduce her later in the series or have her as a per-existing character? UNLESS it's because they needed her to shake hands with Jane.  Plus she is always saying that the supernatural is real, which is something that Red John tries to convince Jane of. Kristina went missing under her protection and is then kidnapped by Red John. A member of Red John's organization who was going to tell Jane Red John's true identity was killed under her protection. Her fiancee was a member of the Red John organization. Bret Stiles said he can help her with her anger. She has red hair (I know a minor detail). And finally in S6, Ep2 we find out that Patrick Jane's Psychiatrist (Sophie) who helped him after his family was murdered, gave information to Red John that he had used to hurt Jane and in that episode Jane finds and listens to her audio notes in which the newest recording (which means the last patient Sophie spoke of before she died) speaks of a female patient with "separation anxiety disorder" sounds to me like the fiancee killing Van Pelt.

Cho, I mean why did the writer have him finish the Tyger Tyger poem unless he was either apart of or the leader of the organization... but this can be easily refuted with the fact that Red John would have no need to bug his own or a member of his organization's desk.