Hello everybody!
As the end is coming, I'd like to share some thoughts after reading all your interesting theories.
Firstly, for me, RJ is an important character in a TV show, so I would like to see him as someone important in the (police) organization, for instances same grade as Haffner or Bertram or Kirkland. I think Partridge and the sheriff and the cop are a little low in the food chain and I'd be disappointed if RJ is one of these. Moreover, as the story goes, RJ seems as intelligent as PJ and honestly when looking at these 3, I don't see any sight of a brillant/intelligent mind.
Secondly, I think RJ might use the tatoo to blame the Blake Association: who in earth would reveal his tattoo on his shoulder when meeting with the female detective? I mean you go to a meeting and dont wear a shirt ? because it's the only way for others to see your tattoo! This leads me to think that RJ might or might not in Tyger Tyger circle but he wants to use this secret organization to serve his purposes. The others in the group dont know who is RJ and like Jane they want to find out who he is. So this leaves out the 3 tattoo cops
Thirdly, IMO, Stiles is a little old and even though his character fits RJ's description, he isn't strong enough to pull off these kind of killing. In the first espisode of season 6, RJ didn't kill Lisbon so it might mean that she is an asset (bugged) or RJ has a thing for her.
For all of these reasons I think RJ would be Haffner. If it turns out that he is Kirkland, I'd be happy as well :-)
