She was 21. She had crossed America on a road trip and was excited about staying in California. But over months, she was living on the streets and struggling. After she trespassed on private property and had a confrontation with the landowner, she was jailed on misdemeanor charges.

Nine days later, she died by suicide.

Alicia Upton was one of 19 people who died in the custody of Riverside County jails in 2022, its deadliest year in more than three decades. That rate ranked the jail system, run by the Riverside County Sheriff’s Department, among the most lethal in the nation, and the second-most in California. The deaths included homicides, drug overdoses, natural deaths and suicides.

Those suicides provide a detailed account of troubling — and persistent — patterns in Riverside County jails that put detainees at risk, particularly those with mental health issues, The New York Times and The Desert Sun found.

Here are five takeaways from the investigation.

The department failed to adequately monitor detainees and intervene when they attempted suicide.

When Ms. Upton was booked at a county jail in April 2022, deputies noted, she was distraught and told them “she always kinda wanted to die.” She was housed in the jail’s mental health unit for women, where a cell camera feed was required to be constantly monitored by deputies/guards to protect detainees’ safety.

One evening, she contacted a guard through her cell’s intercom, but whoever answered hung up almost immediately. The video then captured her saying she would kill herself, and showed the steps she took in ending her life. But deputies did not notice for 20 minutes after the intercom call.