I think that Red John is Gale Bertram. He is a spooky mysterious boss. He makes strange phone calls, and seems to be the most stupid, but he has a lot of power in CBI. I think that Gale Bertram have something strange that makes him the perfect candidate to be Red John. He his working for CBI very close to Jane and he is as much intelligent to avoid being detected by the King of psychology Patrick Jane.

He is tall and strong, and he could have an alter ego called Red John. I think that he frightened Hightower for getting back his job as the CBI director. I always thought that Red John was Patridge because of that special voice. But the less obvious is to be Gale and that would make it more special for Red John, he would lie in Jane's face lots of times and lots of moment would be so special.

Other things is that he is a member of CBI and we don't know anything about him. Girlfriend, married, sons?? But maybe a contradiction is that he is a little old and bald, but he could be the perfect candidate because 10 years have passed since Jane's family death.

That's my theory.