"The simplest answer is usually the correct one"- Patrick Jane

Red John is brilliant, manipulative and controlling. Red John is not stupid and rarely makes mistakes. Red John has followers that help him stay hidden or commit crimes for him. Only they know who Red John really is and they usually end up dead before Jane or police can get it out of them. 
   I see people everyday ruling out Gale Bertram, Ray Haffner and Brett Partridge because they say they arent smart or charming enough to be Red John. In Season 1 episode 9 Patrick Jane confronts a man named Tommy Olds who appears to be mentally-challenged. After Jane exposes Tommy and his act the real Tommy is revealed and he is shown to be a very smart an cunning individual. My point is dont you think Red John would be smart enough to put on an act to fool everybody around him except for those who are his "followers"? 
For example: Bertram played poker and was losing so he got Lisbon and Patrick to help him. Then he started winning. Ask yourself was he really losing because he sucks at poker or was it all an act to throw everybody off? If he had gone into the game and beat everybody dont you think that would cast some suspicion him? 
The same goes for Brett Partridge. At 2 different scenes he said it was Red John when it wasnt and  it wasnt Red John when it was. Dont you think if he got it right every single time it would be a little weird? If he were to stand up to Patrick and challenge him wouldnt Patrick more than likely be able to see through him and expose him? That could be why he always backs down to Patrick. To keep himself hidden. 
   Now for my Theory: Gale Bertram is Red John.
  Yes I know he's bald and according to the height is to tall but I can answer that. Bertam was wearing either a wig or a hair piece. You can also hide your real height by crouching down an inch or two. Especially if its around a blind woman. I also believe That Bertram is way smarter than what he appears to be. The man quoted poetry which just happened to be a William Blake poem and shows that Bertram likes to read. People who read usually are pretty damn smart. Bertram is the Director of the CBI so he holds power and can keep an eye on Jane but also remain in the backgound. Kinda like where's waldo right?
   Now how would he know the names on janes list? Easy! He used Kirkland to break into Janes office to steal Janes Red John Material or Jane's office is bugged and he's been secretly listening to Jane all this time. What about Janes "Happy Mermory" you say? Its obvious that while Jane was locked up in the insane asylum and while under hypnosis or drugs Jane accidentally revealed the memory. The doctor more than likely wrote it down in her notes and Bertram has the file. 
   Also when they laid a trap in the four rooms for the Red John accomplish and Bertram found out he was on the list of suspects he was very very angry about it. He then later knowing That Jane was getting to close tried to make sure Jane went to prison. 
    So with all of that I believe Gale Bertram is Red John.