red john may be kristina frye
no one is expecting red john to be a woman, not even jane, but why not.
it's known that red john has many friends and people working for him. kristina may use one of her friends to talk to sophie miller.any of red john's friends would be kind of weird. 
i don't think that red john is one of the seven suspect. i think that all of them work for red john, but none of them is really red john.
ow, red john has a male voice. well,  that's easy to change with an eletronic device.
and, where the hell is kristina frye? she disappear, i think in season 2, and no one seems to care about her anymore. i think heller left her out of the history so no one remember her.and, before she went missing, she told jane that she is not afraid of red john, maybe because she is red john, or, at least, is a friend of him.
i don't think that red john ever appear commiting a crime on a scene in the show, or that is really him that Rosalind Harker known. it could be another friend of red john implanted to confuse jane, make him believe that red john is a man.
i know that exist many theories about who is red john, i have other theories too, but i think that kristina frye is definitely a suspect to consider. 
what do you guys think?
sorry if a made mistake, i'm actually brazilian.