I think it's gale Bertram because when Jane found out the 3 suspects with the tattoo which was Bertram, Mcallister, and smith one of them is most likely red john. The second episode of season 6 those three were having a meeting. Then when Jane tells them that his mentors head was cut off and put in an oven. Then Jane leaves and reede smith says to Bertram "your the one in charge" . I believe Bertram is red john.