First off, I really don't think it can be as straight forward as being Bertram. 

The show has always been based on unexpected twists and Jane's genius in reading people and working them out. 

So far, the 7 suspects have been whittled down by more traditional "evidence" which is what the rest of the CBI
team usually operate on. 

Kirkland and Partridge removed themselves from the list. 

And then we went from 5 to 3 with Jane finding out about the tattoo. This was more about lucky timing than brilliance.

And then Smith turned himself in to supposedly reveal Bertram as Red John.

So there must be another twist in store. 

Since we've been told we can "trust the list", it still leaves Stiles, Haffner, and McAllister.

Yes, these three have already been pronounced dead, but it's not as concrete as Partirdge's death. 

I believe Red John does have the three dots on his arm, because PJ has said in the past he intuitively knows if it's 
Red John that made the kill.

So if the private investigator that told PJ on her death bed about the tattoo's wasn't killed by Red John, PJ would
have suspected something was out. 

I believe that when McAllister revealed his tattoo, and then said to PJ, "it's not what you think, I'm not Red John", 
that was the moment PJ worked it out. As a master mentalist, he caught RJ in a moment of weakness, and 
knew he was lying. 

Now, when Bertram went to kill PJ in the hospital I believe he was under instructions from either RJ or Tyger Tyger
to kill him. 

Possibly RJ is high up or even the leader of Tyger Tyger. 

When he failed, he knew he could be the main RJ suspect, so he began running. 

The reason PJ put out the media report that Bertram was RJ was the ace up his sleeve. 

He knew RJ could not live with the knowledge that PJ thought he'd caught him. His ego would be too big for this
to happen, so he knew that RJ would reveal himself to let PJ know he'd been defeated. 

That's what he meant when he said he was "letting go".

So those are the reasons I think it's McAllister. The other reason is when RJ is showed on the preview for the next episode
it looks like either Bertram or McAllister. It doesn't look like anyone else. 

And because I don't believe it is Bertram , it must be McAllister. Jane would have never put out the media release because he wants his revenge, he doesn't want RJ locked up) 

And just a few final points. 

Out of the 7 suspects, 6 of them have shown flashes of their dark sides. The real RJ would likely have a very convincing
"act" so nobody could detect his true nature. McAllister has never seemed over intelligent or egotistical. He also seems fairly friendly and a fairly capable Sherif. This is the perfect cover so people would never even think that he could be a serial killer. 

Also, some people have mentioned that he would not be handsome or charismatic enough to seduce a beautiful women like Lorelie. 

When he's acting as his true self though, he's a highly intelligent, powerful figure. One who can lead men and manipulate people at will. 

This type of power would be extremely attractive to women, especially ones like Lorelie who are a little lost. So I don't believe his lack of traditional good looks would account for him being unable to woo her. 

Remember that we haven't seen him acting as his true self as yet! 

So that's my theory. Love to hear your thoughts. Also, apologies if some of these points have already been mentioned!