David Sinclair (portrayed by Alimi Ballard) is a promising FBI agent in the TV show Numb3rs. Since Season 2, David is usually partnered with Colby Granger and tried to stick up for him in "The Mole." In fact, in the Season 3 finale, "The Janus List", when Colby is revealed to be a double agent working as a spy for the Chinese, David reacted with deep pain and blind fury at the betrayal, tears welling in his eyes during Colby's confession just before he attempted to assault Colby in the interrogation room of the L.A. office. Even with the possibility of Colby having been a triple agent and the will to save him, David is not ready to see his partner yet, as he feels he doesn't really know him. Alan has given him something to think about, as Mr. Eppes had said this is a test of true friendship and that he must try to understand his motives. The two are close once more, but only after many failures to cooperate on a mission.
David was assigned to work with Don Eppes in the pilot episode, by the assistant director. By Season 3, he has been with Don three years, and there's nothing Don can't ask David to do. Though, Don worries David may one day realize he's seen too much and leave the FBI. He has knowledge of defusing explosive devices due to his first posting overseas in Tel Aviv, Israel. In addition, David did some work for the Long Beach FBI office.
David's two best friends in childhood were Ben Ellis and Earl Day, as revealed in the episode "Contenders." He grew up in the Bronx, and has mentioned growing up dodging gangs to get an education. He currently lives in Venice, California. Sinclair enjoys Alan's cooking and he is infatuated with medical examiner Claudia Gomez (Lauren Vélez).