Kirkland is Red John. But before that, let me debunk some theories that Lisbon works for Red John (I'm assuming the ludicrous theory that she IS Red John can now be completely ignored because of what Heller said that RJ is one of the 7 on the list).

Firstly, her character - Jane has correctly read that she's someone who's too gullible, can't tell lies, and gives herself away easily. In the S5 finale, when Sean Barlow teased her about her liking Jane, Jane didn't flinch or react much but gave his usual wry, I-already-know-it smile because of Lisbon's nature of not being able to hide anything.

If you think that she's putting on an act then here I come to my second point - her reactions - if you notice whenever CBI receives an RJ case (just like in the S5 finale), her reaction will be one of sadness, anxiety and worry. In the finale, when she received the call from the first responders, as she was walking towards Jane to inform him, she looked very pensive and worried. When they arrived at the crime scene in the motel, she was looking at the victim in great pain and agony even when Jane was not looking. She was genuinely worried and sad for the entire thing and for Jane. And finally when she was watching the video at the end of the finale, she was horrified and looked extremely taken aback by the fact that RJ could make the list.

Think about it, if she was working for RJ she would've known all these and is there any way she would react in those ways?And, for all persistent sceptics out there, even if she IS working for RJ but kept in the dark by all these, do you think she would've lasted as RJ's companion/accomplice after seeing all his murders and heinous tactics for FIVE seasons?? As for her unexplained wrist injury in the finale, I'm sure the producers will come up with something to explain it in the next season.

Now I come to my point about Kirkland as RJ.

Why do I say so? Just look at all the signs that Bruno Heller has been throwing at us.

Firstly, the limo and his voice - in the S4 finale it was made known to us that RJ likes to travel in or make use of limos to communicate with his henchmen. It says a lot about how Jane has been accurately reading RJ as someone to be a showman, who has an inferiority complex especially towards women (a point to which I shall return later) and would thus like to feel good and powerful about himself by killing those who make him feel inferior (women) in cruel mockery (the smiling face painted with victims' blood) and what other way to make yourself feel powerful than hire a limo.

Now Bob Kirkland traveled by limo doesn't he? In S5x05 (Red Dawn) we saw him talking to Alexa Shultz in the limo, watching her carry out his orders to get CBI to feed him info about RJ stuff. Perhaps that's how RJ has gotten all his info about the investigation on him and is always one step ahead? And then there's the voice. From all the 7 suspects none of them have a natural voice that is similar to that of RJ as heard in the S2 finale when he helps kill Jane's abductors. From this we can assume that the voice is put-on. And Heller has showed us in the limo scene in S5x05 that Kirkland is perfectly capable of putting on a high-pitched voice (whether it was accidental, I don't know) when he said "Thank you" to Shultz - is Heller trying to hint to us something?

Secondly, the point I said I'd return to, his behaviour around women - I believe there's a reason why the writers/Heller showed the scene in S5x19 (Red Letter Day) of Lisbon and Kirkland having a chat over coffee - it's obvious that Kirkland has difficulties talking to women, and even Lisbon finds it awkward. But he isn't when it comes to RJ at the end, as he slipped the question in of whether there were any "new lines of inquiry" on RJ - a stark difference from his disinterested, unresponsive and awkward style of talking about growing up and his life, etc. Isn't there a clear parallel to how we know RJ to be as read by Jane - inferior and shy around women, dates a blind girl because he's unconfident and therefore kills women to satisfy himself? And then suddenly he becomes so interested when RJ is mentioned!

Thirdly, other signs - in the episode when Lorelei was killed, for a moment the camera briefly shows Kirkland at the scene looking around, surveying everyone including Jane and looking a tad suspicious from my point of view. Is it because, as RJ, he wanted to revel at Jane's reaction to the fact that Lorelei is dead, mock him for being one step ahead, or perhaps he wanted to keep abreast of the latest developments since it's his "internal matter"? There's also the scene at the end of (S5x19) when Kirkland is in his apartment and he's drinking the same drink that Jane drank during the anniversary of his wife's and daughter's murder!!! Is this a John/Jane parallel that Heller is getting at? Fast forward to the last cutscene and Kirkland is done with his project board on whatever Jane has detailed on RJ's history and the setting is made and the camera positioned such that Kirkland's shadow looms over the board - what is Heller trying to tell us? That Kirkland is responsible for all those murders, responsible for everything, the man who oversaw all of those? And what about the infamous shaking of hand in S5x07 when Kirkland also remarks, eerily, "But I know you" and then one of RJ's theme music play ominously in the background? These are very obvious clues that Heller's throwing at us! And if you suspect that it's "too obvious", perhaps Heller already knows we would be thinking this way and is using reverse psychology on us?

Of course, there's also the theories about Jason Lennon - why did he not recognise Kirkland if he is RJ? Couple of possibilities: Firstly, it may be that RJ (Kirkland) did not give orders directly to Lennon but through some other henchman (perhaps Reede Smith, his possible FBI friend?). Or secondly, Lennon's memory has not fully recovered after being shot or he had been hypnotised by RJ before to the effect that if Lennon sees him in person he's not supposed to recognise him.

Then there's also the thing about the list that RJ made - how could it be Kirkland when he got Jane's investigation trail AFTER Lorelei has died and therefore after they made the video? I believe the answer to this is: Kirkland has always been tracking Jane (remember how he got Alexa Shultz to tell Minelli to inform them about the RJ investigation?) and would therefore know who Jane's met, who shook hands with him, etc. to the extent that he could make a list and narrow them down to the same 7 suspects because like Jane, he would know only who possibly could be at all the RJ murder scenes so far (Jane explained in the S5 finale that's how he got down to the 7). Like RJ, Kirkland would be meticulous and always planning ahead, reading Jane's mind very well because like Jane he is also a Mentalist.

Kirkland also fits RJ's physical profile very well - he's of average height, he's of age to have committed the Visualize barn murders (actor Kevin Corrigan is 44 years old), he has short hair, can put on an odd, high-pitched voice (explained earlier), and he's of relative build to have the strength to carry out those murders. His position in Homeland Security would also give him a lot of access to much information and authority to carry out the seemingly-impossible things that RJ did to be always ahead of Jane. Brett Partridge, on the other hand, doesn't, Gale Bertram and Bret Stiles don't fit the physical bill, it would be too anti-climatic for Reede Smith and Thomas McAllister to be RJ (they're running a show, they wouldn't want to lose viewers), although Ray Haffner can be debatable, but my gut feeling is that he isn't because there's not much emphasis on him in the episodes.

There you have it, Bob Kirkland is the one.