This is not really a "theory" but I just re-watched the episode "Red Sky at Dawn" where Red John saves Jane then recites the poem to him.  But... and I think this is KEY.  When Red John briefly comes back to the chair Jane is tied up in, I am sure he closes his lines with:  "Roll Tide."  I rewinded and listened again and I'm very confident that's what he said!
Then... I replayed the episode because in the back of my mind, I'm pretty sure I heard someone say "Roll Tide" during the episode.  Darn it... could not hear/find it again!
Can anyone verify this because it's the type of surreptitious clue that only a "mentalist" would pick up. 

Red john cannot be a woman like many say. Jared renfrew's message "he is ma" shows that red john is a man as Red John is described as a he.Red john doesn't  believe in god and  he isn't religious. We know this as in season four's finale he tells  jane that " hell does not exist and I won't be punished when I die.  Most people who don't beleive in god often turn to science making Brett Patridge a strong suspect. Brett patridge has only  been seen in episodes where there were copycats of  red john. This is because if he is red johnhe is their to kill them as.He also fits the description given by Rosalind. In season 5 episode 9 we get a glimpse of patrick's note book with the main suspect for red john and brett is at the top. Another suspect for red john is Gale Betrum. This is becassue the assassin sent  by red joohn to kill hightower enters the jote room which only gale knows. We later find out that the assassin carried a rope which she would use to go to the room below whic only O'laughlin knew. Gale and O'laughlin probably discussed about hightower and  realised that they were given two different rooms And the reason the assassin went f to both  Gale's and O'laughlin's room is  because , Gale is red john and O'laughlin works for him or they both work for red john, see in which room hightower was in. Even though Gale doens't fit the description given by Rosalind I don't think it matters as many of the people patrick suspect, we see in his notebook, dont fit the description either like Dean harker who doesnt have short straight hair. 

I believe that bp is Red John because he was at the fake red John murders and has a rapid disliking of Patrick Jane also what red John says s2 last ep if there's 1 thing I can't tolerate is the relentless copying of my work how could he know about that if he wasn't red John

http://www.youtube.com/watch?v=u1F2GdLLoWA

plausible ?!

I think it must be him because he is always there and he sounds like red john, I don't want red john to be Patrick because the story will not be as good.... oh and Bruno if you read this I have an idea for a episode just breath... Patrick gets abducted in his room up stairs of the office at night, the next day Lisbon goes to get Jane but he is gone.. there is a note... well any way further on in the episode Lisbon and the team find the car Jane and the kidnapper were in but the car had skidded of a cliff and it was at the bottom, the driver was gone and Patrick was handcuffed and gaged in the back seat barley breathing, Lisbon calls the ambulance and slightly cries... in the hospital after a few days Jane wakes up finding Lisbon at his side asleep and him with a broken arm........ there you go Bruno my episode there is a lot more to that but you can edit or  add to it as much as you want.... oh and p.s I'm a huge fan of the mentalist and please don't let red john be Patrick :(

To all of you morons out there convinced that Partridge is RJ - do you
really think that someone would create a show in which he would allow
you to solve the main mystery by simply comparing voices ?! And not just
that - but to give you only one guy who has a creepy voice, like that
one of RJ ?! Do you really think that there are only a few of you whose
first suspect was Partridge ?! Are you really that stupid ?! Difference
is, we ruled him out because it would be a lame solution to the show
that is totally opposite of lame. However, he is connected to RJ, as are
Bertram, Kristina and GVP.

Further, the writing "He is ma" was
not meant to be he is Mars or Mashburn, but he is many. Those names
would mean nothing to Jane and the CBI since they meet those two way
later. And as the story develops, we find out that RJ has a net of
disciples, helping him in any way possible, including killing. And can't
you initiate your brain cells just a little bit, and use the mirror
when Lisbon is getting nearer to the bathroom to figure out where the
smiley is, and also realize that it is not the first thing you see at
the scene, because you block that left wall when you open the door ?!
And at the end of that episode, when Jane answers the phone, does the
voice on the other side sound anything like RJ's ? Of course not.

Also,
about shaking hands - it doesn't mean you should re-watch all the
episodes and lookout for the hand-shaking scenes. That wasn't supposed
to be taken literally. In Jane's book, there's a name of Dr Morning, a
"dead" guy. Did you see him shaking hands with Jane ? NO ! That means
Jane met him in his pre-CBI days. He also didn't shake hands with BP,
and yet his name is first on the list. Besides us ruling him out because
that would make the writing of the show bad and transparent, we ruled
him out because of his age and all of the other descriptions of RJ which
he doesn't match. But, Jane himself didn't rule him out so that makes
Partridge a legit suspect. And stop mentioning that scene in which Jane
and Kirkland shake hands. It happened recently, meaning they didn't have
enough time to become either friends or enemies after that. He is not RJ.

If it turns out that BP is ... that would make The Mentalist a laughing stock. So it is safe to say that someone else is RJ.

The voice of Brett Partridge and Red John is an exact match. Cue up Brett's scene in episode one of season one and then cue up the last episode of season two (where Brett also makes an appearance) and listen to Red John speak.
The voice is identical and is the same actor.

Brett is in the first episode of the series but does not shake Patrick Jane's hand in that episode. This doesn't mean he and Jane have not met previously and shaken hands then.
Brett is also in the final episode of season two where Red John saves Jane's life.

Though the voice print is a match and Brett Partridge is in two pivotal episodes of the series, the evidence is circumstantial at best to him being Red John as Brett Partridge has only appeared in two episodes with no more than five minutes screen time for both episodes. He's never shaken Jane's hand on camera and other than the voice match and some dislike for Jane there's nothing else tying him to Red John.

Evidence for:

1. The voice print is a definitive match for Brett Partridge and Red John.

2. Brett Partridge works at CBI and has access to their computer network and servers which Red John has compromised a number of times.

3. He's the same size as the description of Red John.