I think RJ is Kirkland, but Jane has been thrown off the scent because he doesn't appear to have shaken hands with Kirkland.

However, when they shook hands in the past, RJ literally had a different face and did not look like who we now know as Kirkland.

Clues:

1) Do you recognize me? (as Kirland carefully shows his face to the guy he kills in the hospital bed) No? Good. (then calmly injects the needle into the IV).  His voice almost sounded like Christopher Walken, so maybe Christopher Walken is RJ :-)  j/k

2) The woman in the hospital remarks how the guys from Homeland Security are creepy, not who they appear to be, like aliens under the skin.

3) The fake RJ that Jane killed at the end of Season 3 told Jane that he was going to stop killing, get a new face, new identity and move on.