First of all, I would like to state that there are two theories. The first:
He Is MaCBETH
The ones who have read the play will know, that RJ and Macbeth have similiarities in their Modus Operandi: Both awake their victims, see their fear and then cut their throat.
Red John goes by the name of Roy Tagliaferro. Roy, has two roots, the Celtic one which means Red, and the latin one which means King. The historical Macbeth was known as the Red King, because of his red hair. Red hair is something Heller is putting up through the whole show, to every recurring female character(even Lisbon and Hightower, in early episodes have a reddish-black hair glow)
Dean Harken is 43(age of R.J), the actor Tim Curry is scottish(like Macbeth+Odd accent), he fits description, has informatic skills, is very cold blooded, according to Jane he likes scared people, he is member of the CDCA, a fictional agency, like CBI(counterpart of Jane), and he has Friends(it was plural in S2,i.e. O'Laughlin and ?Mancini on my opinion) at the FBI.
The Character of Jane is the Shakespearian Counterpart of Macbeth, Hamlet. Note the similiarity between 4x24 "The Crimson Hat" and Shakespeare's play. Hamlet is also featured in 4x20 "Something's Rotten in Redmund", where Jane plays the Ghost.
The Name, Dean Harken:Dean means Leader of a Cult, while Harken means bowing, obeying, and is spelled same as Harkin, which means Blood-Red color and Pig(at the Elliston farm, the animal shot was a Pig).
The list is not trust-able. I don't understand how did people
expect for Heller to say "Don't trust the list"... It would spoil the
show. And the Characters: Bret Stiles is a reasonable suspect, but it's
my 2nd theory, Bertram, Haffner and Smith are too stupid all of them
played by Jane, Kirkland too obvious, McAllister is long-forgotten,
while Partridge, I think Heller reads this forum and is using Partridge
to ignite the Fans, plus, Red John is cold blooded in his homicides, almost a purist, Partridge gets very exited by blood and violence.
Dean Harken is not a psychic, but his wife(or maybe his sister) Rosalind is. In the ancient religions, blind people had psychic powers such as clairvoyance. In this case, Rosalind is a mix of the characters of Lady Macbeth and the Three Sisters, who push Harken into killing, maybe she is the little girl Patrick and Alex frauded years ago and she wants vengeance.
During the Series, we've had hints of the existence of psychic powers: In the first season, the Witch who bows Cho before the lion(Jane says it's coincidence, but in a later episode he admits that there are no coincidences in the world). Also, Christina Frye is never exposed as fraud, thus leaving only the fact she is a psychic. Same with Sean Barlow. And in a moment, Jane tries to "solve the RJ case in dream", and says to Lisbon Mendelev had seen the Periodic Table in a deam(i.e. psychic vision).
Most likely, Jane had paranormal visions when he was in deep trance(strange how he never uses self-hypnosis to solve the cases). The paranormal phenomenons taking place while in deep trance are known by the old norse as Seidh. Seidh is a woman's magic, and Jane is, strangely a woman's name. Also Jane is too good to be simply a mentalist, he is a little more than that, maybe because he is very good at what he does, too good for my opinion...
