Theories need explanation, for that they are theories. Just saying "Brett Partridge is Red John" doesn't make much of a theory. It does not point out why any other suspect can most definitely not be Red John, and why it has to be Brett Partridge.

I am under the impression that Red John is Ray Haffner. Partridge is a creep and a workaholic. He loved his work far too much, and the honesty with which he said "I am stoked to finally see one in the flesh" in S01E01 is a convincing argument that Partridge is not Red John. Also, try to watch back S06E01. Partridge was lying, dead as far as we knew at the time, on the floor. Lisbon got up, looked at the door and looked back. She was snatched from behind right at that moment. You did not hear a sound which would imply Partridge got up, and he couldn't have done it without making a sound in the time span that he got whilst Lisbon was looking away. Also, he couldn't have kicked her down with his own feet, since Lisbon was standing near his head (she crouched to examine his face, the close-up in which Partridge said "Tyger, Tyger" tells us as much. Also, how would that door open up itself?

In S06E02, the body of Partridge was found. There was no particulars on the body and he was dead alright. If he weren't dead, the coroner would've noticed and otherwise we would've noticed it later in the episodes if the coroner never actually received the body and Partridge is still alive, which would be implication of the situation. Brett Partridge must be dead. I refuse to accept otherwise, it possibly can't be.Partridge wouldn't be Red John. The series have continued after that episode and the goose chase to find out who Red John actually is, is still on its tracks. It would be very lame, not impossible, but lame, if Partridge turned out to be Red John and the whole scene and preparation for the scene at Jane's house were all for nothing.

Partridge is dead.

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I posted this on a theory revolving around Brett Partridge. It does not prove Ray Haffner is Red John, it just rules out one of the most prominent suspects, Brett Partridge. However, I do believe Haffner is Red John. We will see. Please do not rate this theory as a theory to prove why Haffner is Red John, but as a theory why Brett Partridge most certainly isn't.