A Sonoma County judge Friday ruled there was sufficient evidence to try a Santa Rosa doctor who specializes in pain management on charges of second-degree murder in the deaths of four of his patients, clearing the way for a unique murder trial of a physician accused of over-prescribing dangerous combinations of drugs, including opioids.

Judge Chris Honigsberg said state prosecutors had provided enough documentation that Thomas Keller prescribed what the judge called "astronomical levels" of opioids in combination with anxiety medications and muscle relaxants, disregarding patients' other health conditions and ignoring letters from pharmacies and health insurance providers warning of the risks to those in his care.

"The defendant knew his actions were dangerous to human life," Honigsberg said.

Keller, 72, is accused of second-degree murder in the deaths of Sonoma County residents Tripo Nelson, Ashlee McDonald, Dean Rielli and Jerri Lee Badenhop- Bionda, The four charges together carry a potential prison term of 60 years to life.

Honigsberg also ruled there was enough evidence to try Keller on additional charges, including criminally and recklessly doling out medications to another four patients and a single count of elder abuse of a 60-year-old woman who died from respiratory and other health issues in combination with harmful levels of prescription drugs.

The trial marks the first time California Attorney General Xavier Becerra has sought murder charges against a doctor for deaths related to opioid medications. Keller, who suspended his medical practice last fall and was arrested in August, remains in the Sonoma County Jail, with bail set at $12 million. He was indicted by a federal grand jury last year on charges of health care fraud and illegally distributing opioids.

A former Army neurosurgeon, Keller has operated a medical practice on Farmers Lane since about 2008, focusing on pain management since around 2011, according to court testimony.

The judge made his decision after listening to four days of testimony from drug diversion investigators with state and federal agencies, Sonoma County sheriff's coroner detectives and the husband of one of Keller's patients who died. He also heard from a Southern California doctor with pain management expertise who reviewed the medical records for all nine patients involved in the criminal complaint, including autopsy and toxicology reports for those who died.

Agents read from Keller's private journal, in which he repeatedly referred to himself as a "legal drug dealer" and to his patients as "a collection of druggies." Writing about a patient who killed herself, Keller said "psycho b-- girl ... killed herself," according to court testimony.

Keller's attorney John Cox argued the investigation was biased from the start. He said three of the patients who died killed themselves and the fourth death was deemed an accident. The patient records, he said, tell a different story than the one put forward by prosecutors that Keller's actions caused his patients deaths.

"In fact, I would argue the opposite. These were very ill people treated over a long period of time," Cox said.

Deputy Attorney General Tommy Brennan argued Keller treated his patients as "less than human," routinely increasing dosages and combinations of medications to risky and life-threatening levels.

"That's evil, judge," Brennan said. "The motive of Defendant Keller is evil."

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