S2 His red right hand start at 1:11 http://www.youtube.com/watch?v=1otRlA3PedI pay attention to the walk

S6 Black winged red bird start at 3:34 http://www.youtube.com/watch?v=772FU_fAjj4 pay attention to the walk

Also the uniforms are very similar. 

Also he has a possible phobia, very stealthy, self possessed and pretty intelligent, he does meet Rosalind's physical description, his character is meant to be 45 years old so that could put him in the age range for the 1988 barn murders, RJ smells of pine according to Rosalind and McAllister is the Sheriff of Napa county a very rural area, there's the unexplained police car at the end of the S4 finale could be his, plus it would not seem out the norm for McAllister to be walking along those corridors where Rebecca gets killed, it would take a hefty explanation for some of the other suspects (especially stiles) in how they managed to get into the cbi in a police uniform without being recognised/stopped etc.
 
There's probably more that I haven't listed and some of the clues i have given may prove meaningless, but as small/simple as it may be, it's that walk.If it is McAllister, this isn't a clue for the show's characters, it's a clue given to us the audience.

I just think more of our RJ questions are answered and more are easily explained if McAllister is RJ.