A year after being branded by a London newspaper as America’s most lethal police force, the Bakersfield Police Department and the Kern County Sheriff’s Office are now the subjects of civil rights investigations by the state Attorney General’s Office.

Attorney General Kamala Harris, in her final month on the job, announced the probes last week. She cited media coverage and complaints from community groups and individuals about “a pattern and practice of excessive force” in Kern County’s two largest law enforcement agencies.

A Bakersfield police officer’s recent fatal shooting of Francisco Serna, an unarmed 73-year-old with a history of dementia, may have been the last straw.

But the underpinning of the state probes is the unusually thorough and expansive investigation by the Guardian. Its five-part series in December 2015 included videos and links that offered extensive substantiations for its findings.

Kern County Sheriff Donny Youngblood said his agency will cooperate with the state probe. Newly appointed Bakersfield Police Chief Lyle Martin put out a statement making a similar promise.

Their agencies had previously been less forthcoming about possible problems, according to The Guardian.

Police killed more in Kern County than New York City

“In all, 13 people have been killed so far this year by law enforcement officers in Kern County, which has a population of just under 875,000,” the newspaper wrote in December 2015. “During the same period, nine people were killed by the NYPD across the five counties of New York City, where almost 10 times as many people live and about 23 times as many sworn law enforcement officers patrol.”

“One senior Bakersfield police officer has been involved in at least four deadly shootings in less than two years. Another officer separately shot dead three people within two months in 2010. Other law enforcement officers in Kern County have meanwhile been involved in deadly beatings of unarmed men, sex crimes against women and reckless car crashes resulting in criminal convictions.”

The second part of the Guardian series framed the frequent police killings as the predictable result of a police culture in which few if any officers were held accountable for unprofessional behavior and in which citizens who challenged police conduct could pay a heavy price.

Kern County sheriff’s deputies had a confrontation with a 55-year-old man named Scotty Byrket in which “they broke his ribs, fractured his spine and stained his body with bruises,” then decided they had insufficient cause to arrest him. But after Byrket told a reporter about his mistreatment, deputies revived the case. “Byrket was arrested and charged with resisting arrest. He was convicted and sentenced to four months in jail,” the Guardrian reported. “Then, after he was released, he was arrested again and charged with resisting arrest when deputies had first arrested him for resisting arrest.”

The Guardian also noted 10 unarmed men had been killed by Kern County sheriff’s deputies since 2005 after allegedly resisting arrest. None of the deputies in the killings faced sanctions. None of the killings were reported to the FBI and three were not reported to the state, as is legally required. Three were also not disclosed to the Guardian after it made a public records request to Kern County.

Kern County’s coroner found nothing untoward in the 10 men’s deaths. Unusually, however, the coroner is Donny Youngblood, who is also the sheriff — creating a conflict of interest and meaning there are fewer checks and balances on law enforcement behavior.

The Guardian series was an outgrowth of the London newspaper’s attempts to chronicle every police killing in the United States in 2015. Because of frequent links on the traffic-generating Drudge Report, the Guardian has a following in the U.S. and a financial motive to report on U.S. events. U.S. gun violence is closely followed by many British readers.