Reviewed and updated October 10, 2026 by the SearchSystems.net editorial team. The arrest counts are the ones each agency reported to the FBI, as the FBI held them on October 8, 2026. The jail figures are from the Vera Institute of Justice's Incarceration Trends data. Every office link was opened and checked against the office's own site between September 23, 2026 and October 11, 2026.
San Marcos, California, in San Diego County, has about 97,000 residents (2024 Census Bureau estimate). A person kept in custody after an arrest in San Marcos is held at the county jail, run by the San Diego County Sheriff's Office, and the jail's record of each person held is a public record. This guide says where to look for someone in custody, what the jail holds and who books people into it.
This guide covers the search, the jail, who books people, state prison and common questions.
Related guides: San Marcos public records, San Diego County inmate search, San Marcos arrest records, San Marcos warrants, San Marcos criminal records, San Marcos court records, California arrest records and California inmate search.
Finding Someone in Custody in San Marcos
The county jail, run by the San Diego County Sheriff's Office, holds everyone kept in custody after an arrest in San Marcos, from every agency.
SearchSystems opened and checked the jail page of the San Diego County Sheriff's Office at sdsheriff.gov/bureaus/detention-services-bureau/jail-information (page title: Jail Information | San Diego County Sheriff), which answered when SearchSystems opened it on October 11, 2026.
That page is the office's jail information page rather than a roster.
The San Diego County Jail by the Numbers
On an average day in 2025 the jail held about 4,410 people, down from about 6,280 in 2019. Its rated capacity in 2023, the last year with a capacity figure, was 6,180 beds, and it ran at 71 percent of it that year. The figures are from the Vera Institute of Justice's Incarceration Trends data.
San Diego County has about 3.3 million residents (2024 Census Bureau estimate), so the jail holds about 13 people for every 10,000 residents.
Who Books People Into the San Diego County Jail
The San Diego County Sheriff's Office and the agency that reports for San Marcos (filed by the FBI as San Marcos Police Department) make the arrests that end in a booking in and around San Marcos.
The FBI's agency list also places six campus police departments, one other agency, four state agencies and seven state police units in San Diego County (the arrest records guide names each one).
The largest arrest counts reported to the FBI were San Diego's 22,407 for 2025, the San Diego County Sheriff's Office's 4,913 for 2025 and Escondido's 4,830 for 2025.
Together, the 15 agencies in San Diego County with all twelve months of 2025 on file reported 51,876 arrests to the FBI that year. Those kept in custody were booked into the county jail; a person cited and released at the scene was not.
The counts, agency by agency and year by year, are in San Marcos arrest records.
From the Jail to State Prison
The jail holds people awaiting trial and people serving short sentences. A person sentenced to prison in San Diego County serves the sentence in a facility of the California Department of Corrections and Rehabilitation, whose inmate locator is at cdcr.ca.gov/search.
Frequently Asked Questions
How do I find an inmate in San Marcos?
Ask the San Diego County Sheriff's Office; its jail page SearchSystems verified is at sdsheriff.gov.
How many people are in the San Diego County jail?
About 4,410 on an average day in 2025, the latest year in the Vera Institute's jail data, against a rated capacity of 6,180 beds.
Where do people sentenced to prison in San Diego County go?
To a facility of the California Department of Corrections and Rehabilitation; its inmate locator is at cdcr.ca.gov/search.
Is this the official San Marcos website?
No. SearchSystems.net is an independent public records guide, online since 1997. It links to the official city, county, court and state offices described above and does not hold records, charge for them or take requests.