While its obvious that Kirkland is somehow tied to Red John, I think that the fact that he used a green poison to kill Lennon proves that he is actually RJ himself. Remember when RJ poisoned Rebecca? Same stuff. Green poison that killed her in a matter of seconds. My money was on Mashburn until I saw Kirkland shake hands with Jane and say "No but I know you." And I've been flip floppy on which of them it is but now I'm sure it is Kirkland. If he had shot Lennon or killed him in ANY other way I wouldn't think he is RJ.