Partridge's tattoo was cut off after he was killed, presumably by someone in Tiger Tiger. A good reason for this would be if he had betrayed the "club", perhaps threatening to expose them. It was decided he should not carry the tattoo to his grave after he was killed by a Tiger Tiger member to prevent him from talking.
Just before Red John phones Patrick, right after Partridge has been killed, CBI Ron has a phone in his hand, and disappears round the corner.
However, when we hear the audio of the call from "Red John"'s side, we are shown a video of a person at the scene of the murder, with Lisbon/Partridge. He is holding a knife in one hand, and wiping the blood off with his other hand (in a glove) - therefore leaving no hand to hold a phone in.
Therefore, the phone call itself came from somewhere else. CBI Ron has to be the leading suspect for this phone call, and therefore the Red John voice.
That is part of the theory from the perspective of events in the show. Now for evidence we have from elsewhere! Here's a recent quote from Bruno Heller:
"Sometimes you're forced to hate the conclusions or the wrapping things up in silly, absurd ways or in fact — naming no shows — it turns out they didn't have any idea how they were going to end the show or what the secret was or why there were polar bears. We have the answers and it's very important to us, for those people who have been following us from the start, to revealnot in a series of cryptic moments that leave a lot of questions begged. We're going to tell the story and explain who Red John is and what happened and what is going to happen as clearly as possible because the audience deserves that."
An obvious dig at Lost! This quote strongly implies that the writing staff have known Red John's identity for some time. It would be unsatisfying to viewers, and make Heller look highly hypocritical, if someone who had first appeared at least later than season 3 turned out to be Red John. On this basis we rule out Hafner, Stiles, Bertram, Reede, and the Kirklands.
This leaves us with 3 people who fit the Red John description, feasibly, and who have appeared in the show for some time: Partridge, McAlister, and CBI Ron.
Partridge, if the first part of this theory is correct, cannot be Red John.
McAlister in our opinion would be a fairly rubbish Red John. Why not get him back for more episodes in seasons 2-5 if Heller really wanted a satisfying conclusion?
Finally, on leaving the hospital after abandoning his attempt to kill Patrick, CBI Ron is entering the building as Bertram leaves. Ron says "hi Boss" - Bertram noticeably smirks. Because he is humored by the irony that CBI Ron, as Red John, is actually Bertram's boss in Tiger Tiger.
Imagine a reveal of CBI Ron - there's plenty of flashbacks we could be shown.
Lastly, I don't care that he wasn't on Patrick's list. Clearly Patrick has had another list for quite some time that we will be shown. That whole list concept can be blown apart now that the showrunners are basically trying to make us choose between Bertram/Reede this week.
Also, against the list - either this is going to be the worst reveal ever (Smith or Bertram), or the writers have lied to us at some point - either about the list, or the death of at least one of Kirkland/Partridge/Stiles/Hafner.
Just to finish, obviously the promo hasn't shown us anything outside of the first 20 minutes or so of the show, that's the whole thing about promos. It's like the passage on the back of the book - always from the first half. The scenes in the church are Patrick's meeting with Bertram. The "and now you want mercy, after all you've done" quote is obviously Patrick to Bertram (it's fairly clear it's Bertram walking down the aisle). Patrick probably kills him as the Tiger Tiger leader under Red John, doesn't really matter, it's fairly irrelevant. This isn't the Red John showdown.
