Many, many great theories have been posted lately for all the suspects, but I want to put the list aside for a moment and share some thoughts not about RJ himself, but some of his accomplices.

Ive been suspecting Van Pelt for a long time. She has red hair, we know very little about her past. We know her father was football coach but thats about it.

Just now I was on a random episode streak and I end up watching s2ep10. The one with the flashback from Janes carnival past. In the episode Van Pelt is talking a women out of suicide by telling the story of her own sister and the bad decision she made by now sharing with anyone and keeping people away (even Grace). This, in my opinion is something that Jane can pull off and look really truthful, but now Grace. But yet she really look honest to me. Later in the episode when Rigsby asked her about her sister, she denied having one and changed the subject.

Also, in one of the episodes (s1ep16 if im no mistaken) Patrick tried to read Van Pelt and said "you're deeply repressed and emotionally shut down... because of a trauma in your past that you've never spoken of to anyone... ever... even yourself" Van Pelt said nothing after.

But the most suspicious think about her is from the flashback episode of Janes 1st day in CBI. When Grace and Patrick met, she looked like shocked for few seconds. Like she knew who he is, and how easy can read people. Also, she got her job in CBI right after Patrick joined aswell. Like she was putted there to keep an eye on him.

This is a very long shot tho, but you never know. Especially after all what happened with Lorelai and her sister, probably thats how RJ works - he kills the people that you love the most to weaken you and then gets under your skin. Didn't worked on Jane, but worked for Lorelai, maybe Grace.

I don't know, I wanted to share something outside the box, different that the 7 list suspects. Hope you dudes can add something. 

Cheers.