Denzel Washington has frequently said that Detective Alonzo Harris is his favorite character that he's played. He was at first hesitant to take on the role, but one of his sons had read the screenplay and recommended that he accept. Since Washinhton won an Oscar for the role, he has since always accepted every part that his son advised him to take.
During the scene when Jake plays cards with the Latino gangsters, director Antoine Fuqua gave certain instructions to the actors playing the gangsters without telling Ethan Hawke. This was done to further confuse him and add to the tension of the scene.
Tobey Maguire was seriously considered for the part of Officer Jake Hoyt. He even followed undercover narcotics officers in Los Angeles for two months and gained weight for the role. He was dropped when Ethan Hawke, Fuqua's first choice, was finally available for the shooting schedule.
T. Rodgers, the founder of the Black P. Stones Bloods in Baldwin Village a.k.a. The Jungles in Los Angeles, was on-set for all of the filming in his neighborhood, and allowed the producers to use his neighborhood in exchange for casting gang members.