Personally I still believe its Partridge, mainly because this show is one of those where they throw all of the answers to you immediately in a random mess and then unravel it as time goes on. Now I want to make a very clear point here in the latest episode Jane tells Lisbon that he considers her to be a friend and that that rules her out of his list, however if you think very carefully about what he was told, "It's a wonder you two weren't friends the moment you shook hands" That doesn't say they never became friends, and Lisbon didn't like jane from the start as you saw in the flashback, so she is still a pretty decent suspect, and she's extremely close to him, possibly the closest person he has on the planet.
I still don't think it's Lisbon of course, I feel if they did that it would mean way too much hate from the community since Jane and Lisbon should hook up but that's still off track.