I want to say that i realize of something watching every episode again, and i found a person who i think can be RJ, he is dean harken.
I notticed since the first moment he appeared in the show some wear things, the fisrt one, he shook hands with patrick, the second one was he is the only person who calls PJ " patrick" as RJ does not like everybody else who calls him "mr. Jane", dean harken has no photo in his id cdca, i mean if he is the boss in there and someone very important, why he hasn't took that picture.
In one scene he clearly says" i'm gonna call my FBI friends to take care of you" so we noticed he has important friends in there. Also he is in PJ's notebook. And the last one, they didn't like each other since they shook hands, so thats why they didn't become friends.
That's my theory, sorry about my english but i really want to submit my opinion, hope you like it

I really have no idea who it is.  I am just finishing re-watching every episode for the third time.  Every time I feel like I have an idea, there are several reasons to eliminate that suspect.  The show seems to really like the term "red herring", and I believe that any "obvious" suspect is just that ("a red herring").  My best guess is that the person works within the cbi and is close to Jane.  Not only because it makes sense with the story, but will be good for ratings.  
I also think that Red John is probably the actual leader of Visualize and Brett Stiles is just the poster boy.
 I have a feeling that they may have changed the identity of Red John as the series progressed.  A show never knows how long it will be on the air, so I doubt that the first season gave away too many obvious clues.  I think that the 4th and 5th season probably gives us the most info.  That being said though, I do think that the clues in s4 / s5 (if accurate) will hold true to events that occurred during the beginning of the show.  I think that the shaking hands quote is not literal and is a Red Herring.  I do think Jane knows Red John, because Red John would find that amusing.
Brett Partridge fits a lot of the molds and clues, but it does not make good writing sense.  I find it hard to believe that they would make a crime scene investigator the killer.  It follows Dexter too closely and doesn't make for creative writing.
Kirkland is too obvious.
Any of the inner circle would be too far of a stretch.
I have considered Ron for quite a while.  I find that he is a good bet.  There is nothing too obvious and a lot of speculation, but the speculation makes sense in several instances.  He is a Waldo character.  Ron, however, has always had a beard and Rossalind never mentions a beard in her description.  The main problem I have with Ron is the fact that he is so awkward.  I think that the actor who plays Ron struggles.  I find it hard to believe that the will cast Ron as Red John because I think he is going to have to do some serious acting in the final season.
Like I said, I am no farther ahead after watching The Mentalist 300+ times.  All I know is that I will be sad when its done.......but I am still dying to know.  Please just don't fade to black like Sopranos. 

It's hard to speculate at this point but it's definitely not going to be one of the usual suspects and it's easy to rule out most of them already:

- All the dead people can be ruled out immediately.
- Hightower is definitely not RJ, RJ would not run away or be framed anyhow...
- Dr. Steiner is in prison. RJ is not.
- Brenda Shettrick - definitely not, because Red John would never play Volker's informant or anything...
- Rosalind Harker is definitely not RJ because she is convincingly blind. She might be more involved in RJ's business but she is not RJ.
- you can also exclude anyone who is too young to be Red John. Van Pelt, Cho and Rigsby were too young in 1988 when Red John was already somehow connected to Visualize and spent time on that firm. That would probably also exclude Ardilles.
- Minelli is a good guy. LaRoche is definitely not him. Mashburn is fun but he is not nearly sneaky enough to pull it off. Besides, he's too much of a celebrity.

The only couple of people that COULD in fact be Red John from the bunch we've already seen quite a few times are:
- Brett Partridge - he is suspicious  but in my opinion too much of a wuss. I think he likes crimescenes and obscenities but I don't think he could be it.
- Gale Bertram - I found his collaboration with Mr. Homeland Security a bit suspicious, plus I think he was once recited a poem by William Blake to CBI people.
- Bret Stiles - stiles could hypothetically be Red John but it's unlikely.

- Oh and I don't think that's necessary to mention but Jane is not Red John. I mean even if his "search" for RJ was an attempt to hide in plain sight and stuff, his quest to find Red John would be taking it a little too far...
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