i think that RJ is Ray Haffner. of course i'm not sure, but i have some reasons.
first of all, when partridge died, why RJ didn't kill lisbon? there could be different reasons but haffner said in different occasions that he liked lisbon...

moreover, RJ is a person who can act very well, and at Jane's house he was the least suspectable

in addition, Kyra said that RJ had a tatoo, so she had to see RJ's shoulder...but obviously RJ could be aware of this and could hid his tatoo in some way...

one more thing: we have to remember that RJ had a love story with Lorelei Martins...she was very beautiful, i can't see her with Smith, or Bertram or Sheriff McAllister o.O
i think a woman like Lorelei could be attracted only by Haffner or Kirkland...

last thing: Kirkland is dead..but is twin brother?he has never been found...

i apologise for my mistakes but i'm not english :)
i appreciate any comments :)