Ever since the introduction of Kristina Frye, i have doubted her of being RJ. 
There was a time when RJs gender wasnt revealed.  The makers always thought it wise to say "Red John" every time instead of "he" or "she"
However i believe only in season 4 Lorelei says "he" and not simply "RJ"
She might have been misled...

RJ is definitely a manipulator, I dont think only money would actually make anyone do things you want.  There has to be some persuasive powers involved to make someone do it and actually believe that what they are doing is absolutely right.
The only people i can think of who have these persuasive powers are Kristina Frye and Patric Jane.  If PJ is really RJ, then i think it is pretty lame, so KF is my next best suspect.

KF and Patric Jane are more or less adversaries trying to prove a point of whos  best, It gives KF enough motive to keep haunting Jane as RJ and keep him alive to enjoy seeing him being defeated every time

I think KF staged her own abduction by RJ so as to remove any doubts of her being RJ herself.  Its the most perfect alibi.
If she were indeed abducted, why did she take her passport and other things with her? and then why did RJ keep her alive...Keeping Jane alive is one thing as RJ obviously enjoys it but whats the point of keeping KF alive, it just doesnt add up

When KF was recovered, the easiest way to escape any kind of interrogation about RJ was to plead insanity which is exactly what she did.
and then she suddenly vanished.  The very fact that jane has never tried to go to her again and try to stabilise her emotionally to get information about RJ is suspicious
If Jane is trying hard and banking on the smallest of small leads to get closer to RJ, why hasnt he tried to approach KF again to get any info possible on RJ.  If she has really gone crazy, why doesnt he try to hypnotise her and then gather information

The makers obviously are trying to take KF away from the spotlight so as to bring her again suddenly as a big shock and surprise

The Mentalist has always been known for strange twists and turns.  Wht bigger surprise and twist than the fact that Red John is actually a woman !!!

I do suspect Osvaldo Ardiles to be Red John (and no, the person in the picture is NOT Ardiles/David Norona).



At first it's been a hunch I had watching S05E10 ("Panama Red") where I felt a little perturbed about him. I think it's because the man is smiling to much but still radiates something dark. 
So I watched the episodes with him and came to the conclusion that he might be Red John for the following reasons:



- He fits Rosalind Harker's description (short hair, under 6 feet, not muscular but not soft). In S02E23 ("Red Sky in the Morning") Red John is wearing high heeled boots that might let him appear taller.
  Also I remember Patrick describing him as neat/clean/tidy and Osvaldo makes a well-groomed, clean impression.  He seems to be intelligent and cultured. He wears a wedding ring.



- His name is on La Roche's and on Patrick's suspect list.



- As Assistant District Attorney who works closely with the CBI he gets access to lots of information on cases and intimate knowledge about the members of Lisbon's team (like Cho having a relationship with Summer Edgecombe).  I don't know about legal procedures in the US but it seems to me that DA office gets notified fast.  He can come and go and ask questions without rising suspicions. 

I always wondered how Red John did get to Patrick so fast in S02E23 ("Red Sky in the Morning"), he must have known really soon. In S03E23 ("Strawberries and Cream") Red John got to know about the meeting in the mall so promptly he even had time to instruct and send a double. Who did Bertram call as soon as Patrick left his office? The DA?



- Let's stay with S03E23: One thing that didn't make sense to me was the hotel room decoy. O'Loughlin (Red John's mole) and Ardiles had been suspects and given information about Hightower's whereabouts with different room numbers.If Ardiles was Red John he must have uncovered the decoy beforehand. So why still send the killer?  Ardiles might have realised he had to sacrifice O'Loughlin in order to thwart the suspicions against himself. As soon as O'Loughlin got exposed Ardiles was no longer a suspect.




Other observations about him:



- The performance of David Norona is superb, he definitely could pull off Red John. 



- The first time we saw Ardiles was in S03E22 ("Rhapsody in Red") when he interrupted a meeting between Lisbon and Patrick in her office. Patrick did shoo him out for a moment. When he came back his composure seemed the slightest bit off like he had to control himself. 
That's the only time I have seen him like this, in all the other scenes he's in his composure and his acting (if he was Red John) are perfect. Even in disputations he seems totally in control of himself and sometimes even smug like enjoying the game. He is an Alpha animal.



- The whole S04E14 ("At First Blush") is a real treat regarding interaction between Patrick and Osvaldo. There definitely is a chemistry going on. "Ardiles, you got a second?" "For you, Jane, I got two." 

Even while protesting Patrick's interference in his case Ardiles seemes intrigued and amused by Patrick's observations. There is an intensity that's hard to describe. Just watch the episode with keeping in mind Ardiles might be Red John and you will know what I mean. 

Also there is a great scene where he waits in Lisbons office sitting on her sofa in the dark that's got a menacing undertone.




One thing that's unsettled: 


- Does a DA Attorney have enough time for Red John activities? 
Being Red John must be time consuming. In the first season he spent months to build the cellar for the trap.  Also it seems to me Red John brain washes at least some of his followers (and he did mess up Kristina Fye's mind too while keeping her hostage for some time), that needs time as well as his sophisticated schemes.


Please excuse any mistakes in writing, I'm not a native English speaker.

This is a crazy theory but there is a high posibilitie that red John has a very important connection with FBI agent Susan Darcy, considering the interest that she has on knowing about Red John. For example, howcome she was the first person to get suspicious about Red Jhon's death.? It is because she already knew Who he was. It is also weird that when Jane made the trap to catch red John in las Vegas, Susan Darcy started shooting at the car and she was the one that killed agent Luther wainwright , that probably knew red johns identity. Another important fact about that day, is that Red John was actually very near that car, because the phone that was connected to wainwright was a short distance phone. I am not saying agent Darcy is RJ, but she is connected to him. Another interesting insight is that as soon as Patrick finds out that he has met Red John, we can see him writing a list of names at the end of the episode Black cherry, and the name Brett Partridge is on it, but that might also mean we can role him out.