I believed it was Ray Haffner since season 5.  Last weeks episode sealed it for me.  In a previous episode, Jane said that Sophie Miller was horrible and taking notes, so she used a tape recorder and a service to transcript.  Referring to her claim that Red John was "Acrophobic" ( the fear of heights), was actually a mistake of her hand writing.  Her horrible writing re-read it wrong when it should have said "Arachnophobia" ( the fear of spiders).  A simple reveal whne Hafner jumps at the spider.