Red John is most likely a man He appears to be a Caucasian, and is a white person as described by HaleyRed John has an average height: Rosalind described him as "just under 6 feet tall"Red John has short straight hair (as described by Rosalind Harker)Red John either has or puts on an odd, high pitched and soft voiceRed John should be older than 30 years (since his murders date back to the 90's)

So it is obv dexter from another tv show.

I think its the new guy from Homeland Security - Agent Kirkland. He suddenly comes from nowhere and takes charge of finding Jane and Lorelie... wasnt that wierd?

His voice also possesses that high pitched tone of Red John's and there were shots where he was shown getting irritated with all the questioning and interrogation of Lorelie's mother. And 

Gary O'Donnell, CHP Peace Officer guard that Jane tried to hypnotize with a Quarter in "Redacted", but it didn't work.

He shook his hand and acted just like Jane in his manerisms when they interacted in the hallway.

Normally I hate CBI Rob theories but I did notice just watching the season 4 final episode that CbI Ron and another agent do show up with Luther Wainright after PJ has supposed to have killed Lisbon and Rigsby. Next time we see old Luther is in the back of RJ's limo. RJ does tell PJ that "oh you had me going a good while" and that "I have a good friend in the FbI, somI found out when they found out" so perhaps CBI Ron is the mole in the CBI. After last season when they went looking for a mole in the CBI we assumed it was Craig O'L. While he was a mole, perhaps he's more connected to the mole RJ has in the FBI and the CBI mole is separate all together.

Did you ever tought that Red John has never been seen in the series?

Maybe they did not show him to us, just because they may change they enging of the story how they think.
Think about it.

I don't believe any solid identity can be linked to Red John. I am currently catching up (I'm at season 3 episode 12) but at the stage I am at I have reason to believe as of yet he has not been revealed yet. 

My personal opinion is that Partridge is involved and could be Red John's right hand man, the mole inside CBI. It may very well have been Partridge who saved Jane at the end of season 2.  But I do not think this is Red John.  

I will run through my thoughts so far and I appreciate anyone who wishes to speak about the subject to contact me on Jake.Muso@gmail.com.

1) CBI Ron : No, it's not Ron. Would have been interesting but Ron is too much a part of the back ground to be Red John. He seems genuinely not interested in Jane or the team and there would at least have been baleful glance in Patrick's direction at some stage just to annoy watchers into adding him as a suspect.  Accusing him is like accusing a chair on the set. He's part of the furniture.

2) Brett Stiles : I get the feeling that he is most definitely part of the Red John plot.  He basically admitted to it without admitting to it if you know what I mean.  BUT he is not Red John himself.

3) Lisbon, Van Pelt, Cho, Rigsby : In my opinion there is no chance of any one of them even being involved.  There were stages where I believed that Lisbon may be, but her latest behaveour rules her out of it for me.

4) Mashburn : I don't really know about him.  He is a wild card.  But in the end he brags a lot, and he is very annoyingly outspoken.  I wouldn't rule him out as a suspect just yet.

5) Patrick Jane : The notion of him being Red John fits the profile except for the fact that he and Red John are often in two very different places.  I don't see this happening ever.  

However I am trying to look through each and every character to see which person matches Jane in character and skill. Look out for sharp observations by someone other than him.  Because we know they are very alike.  They read the same poetry, they both drink tea, they like playing mind games to defeat their adversaries. Plus if you look at the poetry used i.e. Tyger Tyger.  This is written by William Blake.  In season 3 we see Patrick reading another poem by William Blake.  William Blake believed in Heaven and Hell reconciling and becoming one.  Almost like Yin Yang where the dark and light is one and the same.  Plus the poem speaks of 'fearful symmetry'. This says one of three things:
1) Symmetry as in one object divided into 2 parts which are the same : Making Patrick Jane Red John.
2) The same on one side as there is on the other : Almost like an evil twin somewhere of Jane.  Identical just very bad.
3) As in number 2 there is someone exactly like Jane running the Red John saga.  Someone with the exact same skills etc.  

Plus don't rule out his dad...

I accuse these people:

JJ LaRoche (alive and serving) (fat, no RJ)
Robert Kirkland (alive and serving) (too young not RJ)
Walter Mashburn (alive and serving) (candidate but not probable RJ)
Virgil Minelli (alive and serving) (it suits well the part)
Brett Partridge (alive and serving) (too young and creepy)
Gale Bertram (alive and serving) (too easy but yet it suits the part)
Lorelei Martins (alive and serving)(woman, not RJ)
Rebecca (dead)
Todd Johnson (dead)
Timothy Carter (dead)
Craig O'laughling (dead)
Madeline Higtower (alive? missing) (woman not RJ)
Orville Tanner (dead)
Dumar Tanner (dead)

Those are all Red John but of course there is one among them who is likely the "boss" a good looking not-to-young man. Why? Because his skills till now are far great than those of PJ and my theory is that's because RJ is older than PJ.
In conclusion if you look at RJ as some kind of mentor of PJs abilities then he can be both: Minelli or Bertram

But if you imagine the challange between PJ and RJ as equals then then obvious choice is Mashburn.
Well let's continue   :)

I accuse them of all of being Red John. 
It's not a single person. It's a group.

Timothy Carter said to PJ "I have many names, some calls me Red John".
Also he said "you're seeking a revenge you won't have".

PJ can't avenge because he is fighting a GROUP non a single person.

It's obvious that there's a mastermind who gave the idea: Brett Stiles.

More or less everybody (the males) fit Rosalind's description but I thik she is also in... because she loves RJ so it very likable she won't let him to be caught.

Supporting my theory ---> "He is mar\n" on the bathroom wall.

I believe is it part of the tense "He is many" or the "Mar\n" is the beginning of the name.
Usually when you address someone you start with the name not with the surname. You say Patrick Jane, Teresa Lisbon, not Jane Patrick or Lisbon Teresa, that's simply something we are all used to.

On the other hand I believe that Kristina Frye was the former RJ lover. Who as been left after been useful to his purpose.
To show Jane how deep RJ can control people and how hard he can still hit his feelings, even if he already took away everything PJ loved.

Kristina said "John won't hurt me, probably he is going to change" she is too sure that RJ won't hurt her.
But then she served the purpuse and RJ chose Lorelei as his new lover.

RJ is powerful but not that kind of power you imagine.
He knows how to control people minds and feelings, which allows him to be even a poor man but capable to use very powerful friends.
They prefer to die rather sell RJ.
That's his power. He maybe is even not in PJs list. And if it is then he is the less probable one.