I think it's Bertram. He is very closely involved with Kirkland, who destroyed evidence of Red John when he killed Lennon. Also when Kirkland broke into Jane's room. That's how he got the 7 names and gave them to Bertram.
I used to think it could be Partridge, but it's a bit too obvious and I don't think Heller would want to seem like he's copying Dexter, who's also a serial killer working in forensics.
I don't think that homeland guy Kirkland is Red John because whem they shook hands Lorelei was in prision so there is no way she would know that. And its clear Patrick Jane himself is not the Red John. Red John has appeared in one occasion in front of Patrick. And Lorelei said that Patrick and Red John have met but they are not friends. So we can eliminate more people. But people like Mineli and Mashburn are neutrals but RJ is in 30s so it cant be Mineli. Brett Partridge has soft voice like Red John but I haven't seen him shook hands with Patrick. But they might not have telecasted both guys shaking hands who knows. If anyone has watched Sherlock you will realize something we never has guessed this guy as RJ. Because when we saw Jim Moriarty at first time we never saw that coming. So Bruno Heller should have planned the exact same thing. In the phone conversation between Jane and Red John they used Simon Bakers soft voice for Red John so we can't compare voices anymore like we did with Brett Partridge voice. And I strictly believe Patrick Jane isn't Red John and it's very hard to even guess that would happen. My final pick is Bret Stiles. I don't think that guy has guts to kill a rat even. So no way Bret Stiles have taken lives of 30 victims. And Kristina Frye is a woman. So my point is we know 106 episodes of mentalist have been telecasted. With how many people in those episodes has Jane shaken his hands with? It's hard to count. Red John can be any of them. We still don't have enough evidence to point out who the real Red John is. But I'm pretty sure it's not Patrick Jane