@Parisss, your theory sounded pretty good until you said Det. Marco Francis is a lot like Jane. We haven't seen more than 1minute of this guy, he hardly says a word about anything but the murder and we see no more of him. How you can assume he's a lot like Jane is puzzling. He also looks too young to be RJ. Red John has been a serial killer for 30 years.

None the less, still a good theory I suppose.

The writers of this show are some of the best ever. Everyone seems to be second guessing themselves and also everyone in the show is a suspect! Heller said "Red John is just a man". There is no defining characteristic, hence why we assume it can be anyone.

My assumption is that Jane is RJ, or he knows exactly who RJ is but refuses to tell himself