April 4, 2026 – San Luis Obispo County Sheriff's Office officials issued an updated press release regarding the in-custody death of 48-year-old Trenidad Castilleja that occurred on March 14, 2026.

The Sheriff's Office Coroner’s Unit has determined the cause of death to be the toxic effects of fentanyl, with hypertensive cardiovascular disease identified as a significant contributing condition. The manner of death has been ruled accidental.

Related: San Luis Obispo Sheriff Reports In-Custody Death of a 48-Year-Old Male Inmate at the County Jail

Fentanyl is an extremely potent substance, even in very small amounts. In its pure form, it is odorless and tasteless, making it impossible to identify through human senses alone. These characteristics make it particularly hazardous and difficult to detect. How Castilleja came into possession of fentanyl while in custody remains under investigation.

No further information is available at this time.

Source: San Luis Obispo County Sheriff's Office