I believe that Bret Stiles is the big guy. He's the one in charge, but overall, it isn't just Stiles. Raymond Haffner obviously works for Stiles. Lorelei's sister carved a name into the ground, which can be seen in the murder picture. The name says, "ROY." Roy perhaps could have been 'Ray,' only the 'A' was an 'O' because she was losing her mind-she was dying. Or, perhaps, Roy is another nickname for Robert (Bob) Kirkland. He knows quite a bit about Red John including the information he stole from Jane. Brett Partridge shows the most hatred/anger towards Jane though. So far though, nobody has proved to have the brains that Stiles does. I believe that most, if not all, of the remaining suspects are Red John. Red John is a collaboration of different qualities making him the perfect serial killer. However, Lorelei did state, "I only wonder why you two didn't become best friends from the moment you shook hands." In reply to that, maybe Lorelei only met one Red John.

For the record, I know I will most likely be wrong. I'm not entirely sure who Red John is, but I know it'll only be one guy. The above are just some thoughts.