Hello, i'm gonna say my suspects and why without foreword.

My 1st suspect is Bob Kirkland , Why ?

- The first time Jane's meet Bob but Bob know's Jane ? how is that ?
http://t.co/wzffGZsb

-In season 5 episode 16 we saw Bob tell's to Gale can we trust her? (Lesbion)
-In season 5 episode 18 we saw Bob kill's Red John friend in last min of the episode

My 2nd suspect is Jane , Why
-In episode Red John's Friend's we saw in the last min's of the episode this pic behind Red John Friend
https://twitter.com/WhoIsRedJohn/status/245651198198292480/photo/1/large
-Jane Smile = Red John Smile
https://twitter.com/WhoIsRedJohn/status/252912263814582272/photo/1/large

Done. (;