Edward James Olmos joins Colin Hanks and Mos (formerly Mos Def) for a major season-long arc on the upcoming sixth season of the Showtime drama Dexter. Battlestar Galactica alum Olmos will play a brilliant, charismatic professor of religious studies.  He joins such previous seasonal guests on the show as Jimmy Smits, John Lithgow and Julia Stiles. Production on Dexter begins May 25 for a premiere this fall.