Ray Haffner is Red John.  His background is sketchy.  He looks shady.  Did you see him pull out his notepad when he was interviewing a witness at the gym?  He wasnt even taking notes.  He is a fake investigator.  I am guessing he looks the part with his pressed suits and nice dress shoes but all his credentials are most likely fake.  He spent his late teen and early twenty years being brainwashed by Vizualize, possibly living on a hippy commune farm and starting to act on his lust for violence in murder.  He wasnt playing football or getting an education.  He is a fake law enforcement agent, but he is a real killer.