1. We know Bertram knows Kirkland. Agent Kirkland asks "Can we trust her?" about Lisbon to Bertram.

(a) If its Michael, he's asking "Is she holding out on info about Lorelei Martins?"
(b) If its Robert, he's asking "Is she part of the corrupt group in law-enforcement?"

It is most probably Robert. Because Kirkland says "You'd know better, you've worked with her." And Bertram says "Can we trust anyone?"

2. We know Bertram calls himself seemingly "duplicitous" right in front of Patrick. That's not something a suspect/Redjohn should be saying.

3. We know Bertram wants to be there, when they catch Redjohn.

This all points to Bertram being the Snape of The Mentalist. He's a triple agent. He's actually a good guy.