Jack Kelso is the second playable protagonist in L.A. Noire. He first appears in the first flashback in the game.
Kelso is a former United States Marine and California Fire and Life claims investigator. He became an investigator for the District Attorney's office after investigating the Suburban Redevelopment Fund. Kelso's dislike of Cole Phelps stems from his disgust with Phelps' leadership during the war, most notably at the Battle of Okinawa when he ordered Ira Hogeboom to clear out a cave filled with women and children with a flamethrower. Towards the end of the game, Kelso decides to help Phelps in the investigation of the Suburban Redevelopment Fund.
At the end of the game, Herschell Biggs tells Kelso that he was never a friend of Cole. Biggs then quickly added that Phelps was never his enemy either.
Kelso is a playable character after the Arson case "House of Sticks."