I am not sure precisely who red john is, but my theory centers around 2 key points. 1.) I believe "he is mar" was the beginnings of he is MARRIED. Shortly before O'laughlin is killed he takes back the necklace that he told Grace "it was my mothers." I think that the locket may be a clue to who red john's wife may be, as i suspect o'laughlin to be red john's son. I also believe kirkland to be a son of Red john's, which would put RJ at an age i always suspected, in his 50's. My theory is that RJ's family is a police family, i would imagine at some point Rj was in the FBI and trained his sons and had them placed there. He clearly has training in counter forensics and is always a step ahead, while maintaining access to CBI, FBI, and Homeland security computers, etc. Kirkland asking to be kept in the loop as a favor i suspect was a directive from his father.

I think your theorie has some edge. The only argument i would put
against it, is that he starred in only two (i think) episodes. Which is
not a lot. But for the rest i think he fits the glove.

1. he is
NOT PJ. I think that theory is really bullshit. You cant hold on to a
"fight club" like scenario for so many seasons. Ridiculous theory in my
opinion.

2. All female suspects. It's defintely a he.

3.
anyone within the cbi-team. (and then i mean the close colleagues. They
are far too caught up in catching criminals and much to serious about
it, AND just not smart enough.

So if RJ is a lot like PJ then we need to look at the characteristics of PJ:

he is: charming (especially to women), manipulative, unconventional, nihilistic to a certain extend and playfully competitive,

Besides
that he needs to have a lot of money to organize all these tricks he
played on Jane and i think he should be good looking enough to
accompany his manipulative charms. (Which kinda deletes Laroche and
Minelli for me)

Furthermore he has a fucking big ego (he took
vengeance on Janes portrayal on TV) but i am sure he would charm his ego
away unless he would be pushed to the very limit.

I believe
that no one in real life could really be Red John, and have so much
power over so many people (the only one would come near would be a sect
leader like Styles, which is a little too obvious suspect)

But
if I'd need to pick one on character then i'd also go for Washburn. He
had the same playfullness as Jane, likes to manipulate, likes to
outsmart the other, likes to take risks because of the boredom of
everyday existence (which makes him suitable for a nihilistic  American
Psycho 's Bateman-like character, and has enough time and wealth to keep
Jane busy.

So i go for Washburn too.

So, CBI Ron:

- Ron is a contraction of Red John (Red jOhN)

- A Red John alias is Roy Tagliaferro - Tagliaferro meaning Cut IRON - Ron's surname is unknown, what if it's Tuci!

- The writers were telling us all along - Cut Iron - anagram - IT RON, U C?

- He is observing after Jane fake shoots Lisbon

- Has been in 8 episodes so far, I think, and I read that the writers said Red John had appeared "like Waldo" - hard to find

Question is: did they ever shake hands!

I still think it's Walter Mashburn.  If Red John is so much like Patrick Jane, then Walter fits.  Both of them annoy Lisbon and Patrick likes Walter enough that they could be lifelong friends as Lorelei suggested was likely.  Walter's heart was broken when the woman he loved married Yuri which could have caused him to go crazy and become RJ.  Also, that would explain how he knew to kill Jane's wife to hurt him the most.

Watch the episodes with Walter (Redline and Red Hot), they're full of intense conversations between Patrick and Walter.  Walter says "you'll have to catch me" and that murder is easy if you plan right.  I could go on but out of all the suspects, Mashburn is the only one with the money, power, charisma, and intelligence to be Red John.  He constantly wears the color red and has a powerful/dangerous prescence.  Frankly, I just can't see RJ being revealed as a character that always wears a gray suit and seems to have a dull personality.