I'm unsure of who RJ is, hats of to Bruno Heller but i have my top 2 suspects.

Kirkland and Partridge are dead

Stiles - to old for me, i don't think a 70 year old could strangle and murder so many woman.

Smith - If its him i'd be pissed off, he's fat and doesn't match anything to do with RJ.

Haffner - He's the perfect candidate and i suspected him the moment the list was revealed, i want
             to be surprised !!

McAllister - He appeared early on, he's a good shot with a gun, jokes when he kills someone, 
                  has a good scene of smell, he is around 50 on the show so fits the description of 
                  being middle aged, he was very layed back when Jane entered the room in Ep2 and
                  he's played by Xander Berkeley and i just watch 24 season 2 - he blew me away.

Bertram - He is around middle aged, would have the contacts in other agencies, possibly hiding
               in plain site, he keeps up with the news and the way the CBI is portrayed in it - like RJ, 
               and how would Timothy Carter know to be at the mall if Bertram hadn't told him ? 

Cheers