As two cellmates were fighting in a Riverside County, Calif., jail, an inexperienced guard remotely opened the cell door, a violation of safety protocols. One of the men immediately pulled out the other, hoisted him over his shoulder and threw him over a catwalk railing. He fell 15 feet before smashing into a metal table. It was his first day in the jail and his last day of life.

At another county jail, a detainee who had been mentally ill and charged with child sexual abuse should have been segregated for his own safety. Instead, he was placed in a bunk room with about 15 other men where he was strangled.

When a guard started a security check more than 90 minutes late at another county site, blood was pooling under a cell door and a detainee was wiping the walls. Inside, the officer found the man’s cellmate beaten, stabbed and without a pulse.

Killings are relatively rare in American jails, but those in Riverside County experienced a surge in them. They had the highest homicide rate among large jails in California from 2020 through 2023, according to state data. The murders and other deaths made the county’s five jails the second-deadliest in the nation during that period. In 2022, the jail system’s worst year, 19 detainees would die from homicides, suicides, overdoses and natural causes.

There were clear patterns of security lapses, negligence and policy violations that contributed to the six homicides in the county jails from 2020 through last year, The New York Times and The Desert Sun found. Similar issues were factors in the other deaths from this time period, previous reporting shows.