the real red john is ellis mars. he is a psychic, so he can hipnotize people to do what he wants. and also he is someone almost no one would consider to be rj, in fact, his appearance is only in one episode, and if you see jared Renfrews writing on the wall, you can organize the words as:

he is ma
ehis mars

the double L¨s were badly writen and the look like H.