According to me, Gale Bertram is Red John....
season 3 episode 1...bertram addresses jane as "boy wonder". This proves that he knows about jane's past...

season 3 episode 1...jane says he gets a weird vibe from bertram.

season 3 episode 16...as many people have noticed, bertram quotes a william blake poem...red john quotes a different blake poem in season 2 finale...

season 3 finale...as very well theorized in theory #3183 by BeMyGuest121010, Gale bertram is most probably the reason all of that happened....kindly read it...its very good....and it backs my theory :-D ....one more thing..when jane says RJ has a friend in the CBI, bertram says "this man's a prodigy"...thats classic psychopath behaviour...its thin i know, but still...
Really though, read theory 3183 for proof regarding season 3 finale...

season 4 episode 1...bertram makes osvald ardiles put jane away for as long as possible...i think that's coz he needs time to sort out all the mess like killing that bald security guy, etc....then, when he visits lisbon, he talks with the same calmness and intrigue in his voice as red john....he also tells lisbon to forget about jane....Now, he talks to ardiles and ensures that no death penalty will be issued....we all know that RJ wants jane to be alive...thats why he came to rescue him in season 2 finale....

season 5 episode 14...when lisbon goes to bertram to ask for money for van pelt's computer training thing, he asks her about the poker game...she says"its just a game"..then he reads her just like jane does to others "you dont believe that" he says...

season 5 episode 16...bertram is talkin to kirkland about something when lisbon walks in...as we know, kirkland is MOST PROBABLY red john's associate...
then in the same episode, kirkland is lurking behind the door when bertram and lisbon are talkin about the case...after she leaves, there's the weirdest conversation between kirkland and bertram...he says "can we trust anyone"...he says that with a deranged expression....much like in season 5 episode 13, that father describes that man talkin about the smiley face outside the visualise farm (quote- "what does anything mean")...

finally, season 5 finale.....bertram is on jane's list of 7 suspects....