I would like to point out that there is a 6 year gap between red john killings and i believe that is significant somehow.

My current suspect is Ardiles because he is in a perfect position to be a master manipulator. He has connections and information at his finger tips. He can easilykeep track of where the cbi team go and when they need things like warrents. He is the right build and age group for red john. Also we know red john is connected to bret stiles (i think bret gives people to red join... like desiples) and in the first episode with styles it is mentioned that they had been investigating stiles.

I don't believe it is anyone on janes team. As olaughlin was an infiltrator. Why have olaughlin. If part of the team is guilty. I don't think it is stiles or bertram because their age plus neither likes to get his hands dirty.

I believe even if arsiles isn't red john that red john is someone political