I Think Brett is Red John !! we know that Red John had a source of information From the inside of CBI !! well he need information about the result of investigation of his owen crimes !! so he need somebody who is working on Red John's cases !! So Brett the expert doctor of Red John's Crimes is the perfect cover for the job !! however he must be so clever to fool Jane All this Time Long !! I Hope that My theory be right !! i have not a real evidence but the show let me no other choice.
P.S : Thank you For the idea.
