The San Marcos Detective Division is comprised of 10 detectives who work under the direct supervision of a sergeant. This division supports the patrol function at the station by completing follow up investigations on crime reports initiated by patrol deputies.

When a citizen reports a crime, the first law enforcement respondent is normally a deputy from the Patrol Division. That deputy conducts a preliminary investigation at the scene, collects evidence and interviews witnesses who are present. The deputy then completes his or her report, commonly referred to as the crime report, which articulates the facts surrounding the event. The crime report is forwarded to the Detective Division where it is reviewed and assigned to a detective. The assigned detective is responsible for conducting any necessary follow-up investigation.

San Marcos Detectives investigate cases involving theft, physical assaults (up to murder), sexual assaults, vandalism, burglaries, annoying phone calls and other crimes. Specialized investigative units such as Homicide, Bomb/Arson, Fraud, Domestic Violence, Computer Crime, Child Abuse, Elder Abuse and Narcotics handle those specific crimes for the entire Sheriff's jurisdiction, including the San Marcos command area.

Lieutenant Vince Albini is the Station Lieutenant for the San Marcos Station. He supervises the COPPS Sergeant, the Detective Sergeant, and the Traffic Sergeant, as well as the Administrative Sergeant who is in charge of the overall logistical functioning of the San Marcos Station