No character we have seen in the series is Red John.

This season they have shown us they are pretty much okay with doing flashback episodes that present us with characters that have never appeared on the show before.

All the clues they give, the shaking hands, books and rhymes, it doesn't have had to be shown on the show.
I think they will just keep writing for the character of Red John, completely unrelated to his "real identity".

If the show gets cancelled and they feel like they owe us an episode that concludes everything, they can write Red John in and build a flashback-episode around him and show us 'unseen footage' featuring Red John.

To be hones this a brilliant way to keep the series engaging, one of the worst things that happens to drama series is trying to steer it too much.

I think it is the DA Osvaldo Ardiles.  He is not quite six feet tall, not muscular nor flabby, he has the same build as the Red John who saved Jane from the fake red john movie makers, when Jane was tied to the chair, in "Red Sky in the Morning."  He is intelligent, and has access to restricted police computer systems and case information. I think it could be him. He would be in a perfect position to see if any warrants were to issued for any of his disciples. He was one of the four suspects in the  murder of Todd Johnson who was set on fire in custody at CBI, and the way that Rigsby tried to give the hint  to Ardiles as to where Hightower was, it was lame and besides O'Laughlin had received a better tip from Rigsby. As a DA, he can talk to any person involved with the Red John cases and not seem suspicious.   

Please stop with theory about PJ's double personality!!

-Rosalind should have recognized his voice, his build

-Who saved PJ from fake RJs?

-Lot of people were with him when he was chasing RJ in Mexico

-Lorelai said that he had already met RJ. how did she say so if she knew who RJ is truly?

In this theory there are too many inconsistencies

The theory about Summer as RJ is much more plausible, and that's saying something!!

In the season one finale, “Red John’s Footsteps,” they find
Red John’s lair.  Red John escapes, BUT his fingerprints and DNA (he was drinking a cup of tea) would be all over the house. They
also know he was building something (he ordered supplies), he hung out with his
old partner’s son (the town sheriff), he hung around a small town for at least 5
months, and he sometimes picked up mail at his PO Box.  That seems like more than enough to catch him,
especially for Patrick Jane.   I mean they have his DNA, right!?!

Go back and watch that episode. Can you really imagine Bret
Stiles, Walter Mashburn, or Bob Kirkland hanging out in that dilapidated farm house?



Also, if they have Red John’s fingerprints and DNA, but
haven’t caught him, that means he isn't in the system. That means he can’t work
at the CBI or any other government agency.  



Remember when Red John was just a serial killer. Yeah, me
too. 

In "red queen" Jane tests the protection around LaRoche but putting hightower, his accused and a pawn in his power play in controlling Jane through Lisbon and the CBI team. Jane then uses the entire team to lure him out by manipulating the whole team to go against all of their training and preconceptions of authority into manufacturing the death of Rigsby and Lisbon to lure Red John out proving to Red John that the team won't be blindly lead by a figure of authority and will question every untrusted lead outside their inner circle. LaRoche abdicates his position in fear of exposure.

Second, part of the theory, repitition in the references by Red John's disciples of the poem by William Blake "Tyger Tyger" (again the reference to "red queen" where LaRoche identifies the excerpt being recited by Director Wainright) and Laroche's first names or how they are referred to "J J". His surname "LaRoche" is an easy corruption of John's own name "Red" which can become"La Rouge" french for "the red", John John the red.

From his position as internal affairs unit he can oversee, hear all and see all, on all cases being handled and have access to all files on the team.

LaRoche controls the list of suspects in the Tod Johnson case.

Jane hires Culpepper to steal from LaRoche's house and Jane maniplates LaRoche with what Culpepper finds there.

LaRoche kills the gas station attendant so is capable of killing. 

If that is not convincing enough, LaRoche even looks like the cartoon Red John paints on the wall after he kills.