In my opinion after much thought and observation I accuse Rosalind Harker, why? because truly I do not believe that she is blind, there is no proof. Let's see... Red john likes to play games right? and what better way to really throw off Jane then set up a "blind woman" to pose as the romantic interest of PJ's nemesis, after all he's charming to the women and can make them do pretty much anything. I believe the real RJ could easily have manipulated (maybe even brainwashed or hypnotised) this woman into thinking she is blind because he is clever and cunning and by doing this he could trick Patrick Jane into thinking she actually was visually impaired, thus appealing to his better nature (meaning RJ knows Jane is extra soft spoken and careful when interviewing and questioning people with impairments and disabilities. Truly I believe that Rosalind Harker is the rouse that RJ planned in order to completley throw Jane off his trail.

           Also I have another theory as to who Red John could be. I don't want to believe it, but our culprit could be right in front of our eyes, think about it who is always with Jane pretty much 24/7 and it's here job to keep him in line, yes I know you might hate me for sudjesting it although you could argue about her motive. Also I just had had a sudden thought that occured to me, I don't want to think it because I've always liked her, though wouldn't it be the ultimate  throw off for RJ's identity to be none other than our very own "badass, angry little,pocket rocket, cute as a button Agent Teresa Lisbon? this would explain setting Jane up to play with his emotions, I don't doubt that Lisbon is romantically interested in Patrick Jane, although could you imagine if it was all a plan and Jane fell in love with her only to find out she is Red John and that is why he couldn't "find" 'him" because she was right in front of his eyes. Also there is valid point in this next part, what better way to keep an eye on Jane than by working with him. Also if you think about it from a physchological pov. than wouldn't it be the ultimate rouse to have her as RJ, because no one would suspect the innocent Catholic cross bearing Teresa Lisbon right? also if you think about it from a theological perspective (in catechism) in the Bible it is said that Satan (the devil) likes to play and trick people into thinking he is what he's not, what better way to gain people's trust? I'm doubting this is the case, but wouldn't it be really cool if that was the way the series ended. I again doubt Bruno Heller thought about that one, although that would be awesome! (I should have created "The Mentalist" :)
or another interesting end Angela and Charlotte are behind it, and Jane kills his wife because the wife forced Charlotte doing her dirty work for her while she sat back and watched, so Charlotte was RJ and Jane was trying to catch his daughter! ........naaaaah, lol!

Also I don't want to believe it though patrick Jane could possibly have suffered a nervous mental brake down after his familie's death to the point where he actually went insane, and he's got a double life. (I'm not ruling him out yet because he's good for it! every scene adds up! the one I most analysed was when Jane was in the Hospital and they were pumping his stomach after he consumed Bella Donna in his tea (the hallusionation of his Daughter talking to him, I found it strange the way that she said to him "Does anyone know who you are?" almost like I know what you've done and I not happy about it, to which he replies "Yes.' then Charlotte asks "Who?" then Jane is quiet and then after a moment he says "Lisbon." then the flash back to Hospital starts and he is calling Lisbon's name.

You know personally i believe around season 4 Jane proved to himself that he know the true identity of Red John, now I just believe it's a matter of time and convincing the other's at the cbi that he actually figured it out.
I believe that he just setting the stage now for Red John (hopefully) to walk right into it, because given the information he has learned of RJ he is now baiting him to catch him, even though Red John and Jane are supposedly one in the same and very symmetrical, there is one part of the bigger picture no-one is seeing, Jane has to sneak up on RJ when he is most vulnerable and he needs the tools to do it, though they are both genius one will eventually outsmart the other, Jane knows the way he operates and excites things so it's just a matter of setting up the stage for what will hopefully be on of the best reveals in tv. History! RJ thinks Jane is completely off the mark, although really this whole time he's set the stage (the witnesses, the victims families etc.) there is most definatley a bigger part to the story and I believe since Jane started in the cbi from season one to now five he set things up for a reason in order to uncover the identity of the "monster serial killer" know simply to the audience as RED JOHN.