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!