Well, I guess the best way to sort this out would be to rule out all others, as Jane has done. And let me just say out front, I don't have any doubts on the fact that Patrick Jane is not Red John. The entire point of the show is about a damaged and angry man looking for justice. It would not make sense at all for him to be Red John. 

1. Brett Partridge- yes, he is sick and "ghoulish" and maybe even a little sadistic, but I think he is too young to be Red John. It says in the episode "The Red Barn" that Red John was a teenager in the 1980's at Ellington farm.Red John has been described in numerous episodes as a middle aged man- something Partridge is not. He can't be more than late thirties, which is the wrong age for Red John. 

2. Brenda Shettrick- there are a number of reasons why I think she isn't red john; she is now behind bars, and Red John promised the he would be killing often; she is a SHE, and all the named confirmed on Jane's list were male; she was sloppy and panicked in her final episode, something I do not believe Red John to be. 

3. Brett Stiles- hmmmm. he is a little trickier. But I don't think it's him. First of all, as with Partridge, he is actually doesn't fit the Red John timeline. He is too old. and although red john seems to be either a previous or active member of Visualize, Stiles is an integral member, a permanent masthead. Red John also likes to be close to Patrick, as another user mentioned, to watch him suffer. Stiles doesn't appear in the show often enough for this to work. Although I have no doubt he is somehow connected to Red John, i don't think it is him. 

4. Reede Smith, Sheriff Thomas McAllister- although creepy in their own right, both of these characters seem to vague to me to be Red John. Although we don't know who he is, I think he is now a relatively important member of Jane's life, and both these characters have not appeared often enough for this to hold true. 

Hang in there, I know its been long; There are three remaining names to be considered... Gale Bertram, Ray Haffner, and Robert Kirkland. There are actually three very viable suspects: They are within the age of about where Red John should be, are a close part of Jane's life, and there have been sizable hints given about each of their characters. It was hard for me to choose, but I went with Kirkland for a few different reasons. He, to me, seems the most interested in Patrick's life; he talks to Lisbon about him, and seems to actually have a keen interest in the case of Red John, something odd since Homeland Security doesn't usually handle serial killers. He broke into Jane's attic workplace to find out what he knows, and he seems to be pulling the strings a bit with Bertram. 
Anyway, yeah. I think Kirkland is Red John. Let me know what you think of my over done rant! 

Episode 19 Red Letter Day proves in my eyes that Bob Kirkland is a strong contender to the title of RJ. The episode shows Kirkland's Homeland security boys break in and photograph Jane's wall of suspects. The final scene fades Jane's board to that of Kirkland's copy as he pins the last copied documents to it. This symbolises the final peice to the the puzzle of RJ's identity. Immediatly after a high angle shot of the board is shown with Kirkland's shadow perfectly filling the board, the shot then changes to a medium long shot of Kirkland standing in front of a window and his shadow still covering the board.

This shot is far to constructed to be coincedence. You will notice that it appears that the shadow is created from a bright outside lights, perhaps a full moon. However the balcony is in clear view and remains in the dark. Furthermore the room has too lamps to either side of Kirkland that would eliminate the harsh shadowing over the board even is the outside lighting was acurate.

The use of this imagery of Kirkland's shadow is extremely simple and perhaps to obvious to make Kirkland a serious contender to be RJ, but still it cannot be ignored. Episode 19 is foreshadowing in both the literal and literary sense.

Connections can be made through the use of this imagery that prove kirkland is not RJ. One of those being that Kirkland is helping in the search for RJ and that the shadow represents that he is 'hot on the tails' of RJ, that he is 'lurking in the shadows'.

I believe that this final scene from Episode 19 is perhaps the most important single image of the entire season, in the sense of giving a solid clue as to RJ's identity. The deliberate use of such a photographed and structured final shot is proof that Bob Kirkland the strongest suspect to be RJ.

Hmm..in The Red Barn we must remember that Jane eliminates those not associated with Visualize...thus can we conclude that all 7 have some connection with Visualize. 

Just a thought....could Robert Kirkland be Miranda's boyfriend? Maybe he is after rj himself for killing miranda and asked jason lennon if he knew who he was because jason would have seen him when he took miranda away.

It has to be Bob Kirkland because in one of the episodes, he went to Teresa to tell her to stop following Volker. On the way back, he bumped into Jane saying, "Sorry Jane." Jane asked, "Do I know you?" Bob replied, "No, but I know you." Bob had a smirk on his face. They walked away. While Jane asked who he is, he was shaking hands with him. This was episode 5 of the fifth season, If it Bleeds, it Leads. In one of the episodes when Lorelei broke out of prison, she said that Jane shook hands with red john. Jane and Bob shook hands before the episode when Lorelei broke out which was episode 8 of the fifth season, Red Sails in the sunset. In the season five finale, Jane was down to 7 suspects. One of those was Bob Kirkland. He has to be Red John!

Someone just mentioned that when Patrick was rescued by Red John in season 2, Red John asked: Do you know who I am? The same line Kirkland was asking Lennon before he killed him - coincidence? Maybe. However, Kirkland proved he is not afraid to murder.

in a couple of episodes we have seen people from patrick's carny life come back and confront patrick
about him lying and for taking their money...do you remember when patrick was in vegas?...so this theory somehow
can be true...i dont know if we can actually say her identity could be rj....but it can definetly play a part in the series.
let's
say for the sake of argument that teresa is the little girl...we know
that her mother was killed...some think it was a drunk driver,but we
don't know for sure..what if somebody killed her mother because of the
rock patrick's father sold them.maybe somebody killed her mother after
learning the price it costed them and that person thought it might be
worth reselling it.or maybe
lisbon's father killed her mother when he
was drunk and after learning how much she spent on the rock...thus
making patrck guilty and thus giving teresa motives for revenge..the
little girl might be rosalind or vanpelt...everybody has secrets...THERE
ARE SO MANY GREAT POSSIBILITES WHEN IT COMES TO THE REVEAL OF RJ'S
IDENTITY...maybe we are over thinking it..I wished they could have
explored the characters a bit more instead of only showing up like once
or twice a season....in an effort to keep some of the characters a
mystery just to keep us guessing they failed to explore the characters
life wether in the present or past...would have been more
entertaining...how can the audience take the show seriously when they
have so many characters come and go...and then have suspects like the
sheriff as possibly being red john,,that;s just a slap in the face and
lazy writting....bruno can pick anybody he wishes AND IT WILL MAKE SENSE
because that's how the show is set up..HERE'S SOMETHING ODD since the
show's beginning it has been set up as rj's identity as being a
man..FIRST MISTAKE in my opininion...even though a lot of fans thought
it was a woman at the beginning i think they should have given us some
clues to point to the identity possibly being a woman...rosalind
description took a lot of the fun away...HERE'S  my opinion..to me it
would have made sense to have a woman in the final 7 suspects just to
mess with us and make it a bit more fun...my opinion?...they are
probably waiting for season 6 right before the revealed to play with
this possibility...after all do you remember lisbon asking jane if she
was a suspect..he is probably keeping that possibility to
himself...patrick being as smart as he is...after burning rj's files so
many times why would he make a list and then show it to somebody unless
he has a plan and is not telling anybody not even lisbon...i think he
will use her somehow....when it comes to writting a tv show I DON'T KNOW
SQUAT!! ...but common sense would suggest that next season a woman
could come up as a suspect as to being the mastermind behind
rj..EXAMPLE..bruno heller could pick any fool to be rj...let say for the
sake of argument REID SMITH..his identity is not that exiting or makes
sense at all BUT...if he reveals a woman calling the shots behind
rj...let's say...TERESA LISBON..or even GRACE VANPELT....just the tought
of patrick confronting either one after he realizes the identity makes
it that much exiting and worth the wait...just because the audience wants patrick and lisbon to be together doesn't is going to happen for sure..bruno said that they feeling will emerge in season 6 but never said in so many words they might end up together...there are rumors of the show not being cancel after they catch red john.i can see lisbon being killed and patrick taking her job...think about it if patrick catches rj..this has CAREER MAKING EXPERIENCE written all over...thus making patrick cbi senior agent patrick jane somehow.