We don't know what happens to Patrick's father
I have a theory: I think he's Bret Stiles (his past is doubtful), and Red John!
This is his father who taught him Mentalism!
My justification:
"In the mid-1980s, when Patrick Jane was 16, he worked in a carnival as a psychic boy wonder, with his father Alex who MC-d the sideshow. Patrick had what his father called "x-RAY eyes," his amazing skills of observation, deduction and induction. He had a rough existence with his father, the only adult in his life, whose treatment and use of him was tantamount to child abuse. When Patrick refused to scam a dying girl and her grandmother, his father threatened him and forced him to do it. Jane later said that he never went to a high school, presumably due to the nomadic carny life. "
http://thementalist.wikia.com/wiki/Patrick_Jane
