He is many. Specifically an organized group with one true killer/mastermind and dozens of other followers and pawns willing to kill and die for him. If red john has to be one of the 7 suspects I'll go with bertram; however, kirkland, stiles, partridge, haffner, and minelli are his friends and main accomplices. Here's the evidence:

1. The actor playing Bertram was born in 1962. He'd be 26-27 in 1988, the possible first Red john murder. Most serial killers commit their first murder at an average age of 25-27. The timeline fits perfectly. Could easily be involved with visualize and stiles and haffner at this point.

2. Bertram is manipulative and deals with media at the CBI. Note that red john is very concerned with his image in the media and how he's portrayed. Just like Bertram.

3. Bertram might fish with minelli and could have met Jason Lennon while fishing as well. Explains their friendship and connection. We also don't know about Bertram's past or life like we do the other agents at CBI.

4. Alexa Shultz worked with Bertram and seemed uncomfortable around him. Could be an act. She's also the one telling minelli about jane's stay at an insane asylum at the request of Kirkland. If minelli and Kirkland are working together and reporting to Bertram then they could easily track down Jane's therapist at the institution and hypnotize her to get Jane's memories, feelings, and mannerisms. This is how red john knows Jane's happy memories. He doesn't have special powers he's just messing with Jane and jabbing at his confidence.

5. Bertram was with Jane which is how he knew where to tell timothy carter to meet him at in the season 3 finale. Also Bertram disappeared after Jane went to confront him along with the red shirt guy. Another follower possibly.

6. When he kills he leaves no evidence. Is it because he's really good or because he has Brett partridge, who's always the first at the scene during red john crimes to come in and clean up making sure all evidence is gone by the time everybody else gets there. Remember partridge said he was working on red john murders since he started.

7. Lisbon's been acting weird lately. Like she's might be an accomplice. As a matter of fact ever since she started playing poker with Bertram and the others. You do the math. They've gotten close, Lisbon seemed worried Jane suspected bertram, and has been really prying at Jane trying to get any clues. Keep in mind red john seems to find out a lot of info about Jane's plan that only he and Lisbon were aware. I smell a rat.

This is my theory as how Bertram could be red john and how he'd pull it off with his accomplices. Let me know what you think.