I think that chapter 2x08 teaches you a lot, and by paying attention to that chapter in particular theres a lot of things you can disregard, and options that you can exclude as early in that chapter, for example.

1.- For those who think that PJ maybe RJ, this chapter pretty much refuses 99.99% of possibilities, it cannot be PJ since he interviews rebecca and then RJ poisins her, you can see in Rebeccas face that shes facing love, shes facing whoever RJ is, so im 99% sure we can forget about RJ being PJ.

2.- Even tho is technically possible, is really hard that minelli is RJ, since he was in the questioning room in a suit, then few seconds later RJ is in another part of the building dress as a police guard, and if he was minelli, somehow the other policemen cound have seen him or recognized him, this also makes Ron a higher suspect, since from the body build that you can see from the back of red john and the fact that he could be there in the building at that time then change and go to his regular place, increases the chances.

3.- Again, from the body build of RJ in the police guard uniform, you can easily asume that is not laroche, and that is not Stiles, and that it should be someone that could remain in the building by changing his clothes and be hiddin in plain sight.

4.- In my oppinion, the producers are playing us and damn they are doing  a great work, we are as obsessed to know who RJ is as the same PJ itself,  if you ask my oppinion, the producers are on purpose making kirkland one of the main suspects, basically so we rip or heads off by saying, "He cant be, is too obvious" or " he must be, is so obvious", either way, kirkland is Red John, or is hunting Red John or is a part of Red Johns Web, one thing im sure, Kirkland is going to be the key to reveal who RJ is, the best way to keep us interest in the show for next season, is revealing who red john to us in this season without letting PJ know, so we can be waiting for the next season in pain waiting to see what would happen...

Well, This is my 2 cents, Who is RJ? at this point is completly useless to make a guess, somehow even when we find out, a lot of ppl will not be happy with the decission and we will find loose ends everywhere, probably because on the first seasons not even the producers knew who red john was.

Almost sunday and hopefully one day closer to figuring this thing out.