Captain Trevino is second in command in the San Fernando Police Department, reporting to Chief Valdez. Trevino supervises Detectives Bella Lourdes, Danny Sisto, and Oscar Luzon. He carries a number of other responsibilities as well. He is in his mid-fifties. He has a shaved head and a mustache. He usually wears a uniform while on the job, even though he is in charge of the detectives who usually do not wear uniforms
In 2016 when Harry Bosch began working as a Reserve Officer, Trevino was skeptical about the arrangement. He tried to micro-manage Bosch by insisting that he sign in and out and follow other bureaucratic procedures. Over time, Trevino came to respect Bosch's skills, and he relaxed somewhat in supervising Bosch.
In October Lourdes was kidnapped by the Screen Cutter rapist. Bosch led them to the home of Kurt Dockweiler whom they placed under arrest. Trevino questioned Dockweiler, but in the process the suspect pulled a gun on Trevino, Sisto and Valdez. Bosch shot Dockweiler, saving the lives of Trevino and the others.
Susequently, Trevino asked Chief Valdez for authorization to hire Bosch full time while Lourdes recovered from her injuries. The Chief approved and Trevino made the offer to Bosch who accepted.