Robert Kirkland is RJ. Why? First I would like to say why Patrick isn't. Simply, because Lorelei said "the moment you two shook hands". She knew both of them and she knew he is someone else.
For the very same reason, it has to be someone who shook his hand with Jane.
Kirkland did it. Kirkland also was the one who said "thank you" on the end of the episode showed us Patrick's beggining in the CBI.
And after the very last episode: Kirkland is a murderer, a one who have done this before and murdered because he was afraid to be identified. As who? As Red John, of course!
How is Brett Styles getting into the picture? I would speculate he might even be related to Kirkland. His father, maybe. This is the reason why he knew about what RJ is about to do but didn't handed him to CBI.

I think it's Robert Kirkland, because he was in the limo with Alexa when she made the call, and he works for homeland security, but he's never given a reason why he was interested in Lorelei. Also, he asked Jason Lennon if he's ever seen him before, and said he was a "friend".body {background: #3A3636 !important;}div {background-color: #3A3636 !important;}header,nav,table,th,tr,td,dl,ul,li,ol,fieldset,form,h1,h2,h3,h4,h5,h6,pre {background: transparent !important;}* {color: #B6AA7B !important;}a:link,a:link *,a:link:hover,a:link:hover *,a:link:active,a:link:active * {color: #B6AA7B !important;}a:visited,a:visited *,a:visited:hover,a:visited:hover *,a:visited:active,a:visited:active * {color: #D9C077 !important;}

What about Robert Kirkland from season 5, episode 7. They make a decent deal of the handshake on camera and 'Bob' said he knew Jane. Loralei said that Jane had shaken hands with RJ..so maybe? RK is interested in the whereabouts of Jane and Loralei (s5ep8) and he works for homeland security, so could have all the high up ties. He's the right age also to have been at the farm. Thoughts?

Here are a few theories on Robert Kirkland. I don't think that he is RJ, and I think that him getting a facelift is absurd. I hope that the writers wouldn't do that to us the viewers. But I do think that he is corrupt in some way. 

1. He is an accomplice of RJ. Probably very high up, but rarely seen because of his deep cover in Homeland Security. He may be RJs right hand man, even. He was seen by Jason Lennon once many years ago, and RK asked Jason if he could recognize him. Not because he has a "new face", but because he could have blown his cover and wants to be sure that no one else knows who he is. If Lennon had known who he was, RK would have had to kill the people he had told about RKs true identity. He kills him anyway because he is ordered to do so by RJ, so that Lennon can't tell Jane who Red John is.

or

2. Robert Kirkland is/was involved in the operation going on at the shelter and bought one of the women that were being sold. That would also explain him wanting to know if Lennon could ID him and thus know if he had told anyone about RKs corruption. RK then killed him so that he wouldn't tell PJ or anyone else about his involvement in the operation at the shelter.

or 

3. Both. RK is Red John's right hand man, but was never seen by Lennon until he bought one of the women from the shelter. Not knowing that Lennon worked for RJ at the time, he didn't use a disguise. So RK had to make sure that Lennon didn't recognize him so that he didn't tell anyone (especially RJ) about his involvement with the shelter. This would both cost him is job (and cover) in Homeland Security and probably his life from RJ for making mistakes.

Those are my theories on RKs involvement. Hope you like it!

I think it is Robert Kirkland, and for anyone who has seen the last few episodes, it seems quite plausible. I mean, the whole scene where he kills the guy in the hospital saying "I'm a friend"..... and when he met Patrick Jane, he looked at him and said "Hello Patrick", and Jane looked at him and said "Have we met?". Kirkland's face then changes quite drastically and introduces himself. Something about him, I don't know, it just isn't right. 
Well, that's my guess anyways!

The last episode shows us how Robert Kirkland mercilessly kills Jason Lennon, making most of us think he is RJ.
But what if he was avenging the death of Miranda? What if he was in some ways related to Miranda and Lorelei? Remember he made his appearance only after Lorelei escaped from the prison! Just a thought! Please let me know what u guys think :) 

Hello, i agree with Robert Kirkland as Red John killer.

The first time i saw this guy, i wonder "is he a freiend of RJ ?"

With the last episode and the dialogue between R.B and the other guy, let me think he's RJ. P. Jane may think the same when he look after him...

Sorry for my bad english, i'm french.