Of all the remaining suspects, you can make a case for any of them. Some are more tenuous than others, but this is TV, so they can always squeeze a round peg in a square hole if they (Heller) want to. Eg: Stiles is too old, but you can massage the facts a little and make him work. Bertrum is bald and seemingly not physically equipped to be RJ, but again, it is possible. However, of all the facts we now know, Haffner fits all of them. He is by far the most likely. Reasons:

1. He is similar to Jane. He even looks a little like him. He is charming and physically stong and agile. This is VERY important and not to be overlooked. RJ is a guy who can charm women and men alike into being accomplices that view him as a deity figure. They would die for him before betraying him. RJ would likely be good looking and incredibly charismatic. All the time. Think of Lorelei and the kind of person to completely have her under his spell (not to mention all the others). She says RJ and Jane are very alike, and surprised they didn't become friends after shaking hands. The most alike Jane amongst the suspects is Haffner. By a mile.

2. Physical attributes. Height. Age. Hair. And also his strength and agility. RJ is a guy who doesnt just kill with a gun, he slices up people. He hides in bathrooms and sneaks out behind Lisbon to accost her. He is strong enough to slice up Partridge, bind him, put him in a closet. All the men could do this, but it is just so much more likely that RJ is physically very strong and agile. Haffner looks to be the best candidate again. Perfect height, age, hair for the descriptions. Fit, strong, agile, very capable of the physicality of his murders and the murder scenes he constructs. Much less so are Bertrum, Reede, Stiles, Mcalister.

3. Whistle. As soon as Haffner whistled that tune after the creepy hospital visit I thought it would be very meaningful. (Anybody know the tune? is it a clue?) And then right on cue, we learn from the shrink who overheard RJ whistling in the waiting room that RJ is an excellent whistler. Note: he whistles in a waiting room at the shrink's. So he whistles at odd moments. We hear Mccalister whistle in the car, but this is normal behavior. Whistling in a waiting room, a little less usual - just like whistling as he leaves the hospital room. I mean, it was just so odd that he started whistling. Who does that as they leave a hospital room after an awkward conversation. Perhaps the 'phobia' that the psychiatrist detected was a phobia of medical rooms? Silly, i suppose, but something to think about. Whistling at the shrink's office and also at the hospital.

4. He either genuinely likes Lisbon or he is trying to woo her as part of his plan to mess with Jane. Either way, RJ did not kill Lisbon and Haffner fits this criteria too.

5. Power, connections, technology: Haffner's job and status gives him all the ability to monitor and control the situations as he needs to. Perhaps not as much as Bertrum, although perhaps in some ways he has more power, given his elevated federal status.

6. Visualize connection.

We still need to discover the Blake connection with Tyger Tyger. We still need to learn more clues, and likely twists and turns will occur. But as of right this moment, who is more likely than Haffner? He just fits the physical facts so perfectly.