I reckon it's Jayne. I think Jayne has a mental disorder and is actually Red John. It would explain the fact that Red John is apparently 10 steps ahead of them all the time, and it would explain why Red John seems to know what Jayne is thinking about before Jayne does.
Jayne is a very talented Hypnotherapist, he could hypnotise people that know his as Red John into thinking he isn't Red John.
Seriously I think Jayne IS Red John!
