Hi, I have 3 good reasons as to why Brett Partridge isn't RJ.

1. Brett isn't smart enough to be RJ. RJ is just as smart if not smarter than PJ. Refer to season 5 episode 15 where patrick had to tell Brett that it was murder and not an accident. Even if you said RJ didn't want to possibly reveal himself to PJ it wouldn't make sense because that case was completely unrelated to a RJ case.

2. RJ has too much pride to let another person take credit for his work. Refer to season 1 episode 1 where Brett says, "classic Red John smiley." Now you might say he didn't want to give himself up or that he wasn't saying it was Red John just his smiley. which takes me to reason 3.

3.As established by Red John killing Patrick's wife and child he hates being insulted especially in public. So if Brett was RJ why would he let Patrick get away with insulting him in front of people multiple times? Even if you said he "likes" Patrick and doesn't want to kill him because he has fun with him would still not make sense because he could easily have killed Lisbon, Rigsby, Cho, Grace, or anyone he's close to to get back at him.

Thanks for reading my theory! Thoughts?

I think it's a CHP officer. They can easily access helicopters, boats, fast cars, and motorcycles to get where they're going quickly all across California, Nevada, and Mexico. Same places red john has killed. I believe the HQ is in Sacramento which is where most of the rjk have happened. Plus Jane shook hands with chp officer O'Donnell and couldn't hypnotize him. For one episode it was all about their interaction. He may be a red herring but I definitely believe it's someone from the California highway patrol who's in with visualize and friends with a lot of cops/FBI in visualize as well. It may even be Bret stiles' son.
P.S. the one who killed Rebecca had a chp uniform on and was in the same holding area O'Donnell was in if I remember correctly.

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.