We've already seen Red John. It's the "FBI" guy who was on the few episodes when Jane helped Lorelei escape. He's the man who went with Lisbon to interview Lorelei s mother. Remember when the FBI woman was on the phone with the man in the limo?? She said "it's done". You see him briefly in the limo. That's who it is! He also shook Janes hand in the cbi