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LOS ANGELES — A Los Angeles-area doctor was convicted of murder in a landmark case for killing three patients who overdosed on what a prosecutor called "crazy, outrageous amounts" of painkillers she prescribed.

The second-degree murder convictions Friday of Dr. Hsiu-Ying "Lisa" Tseng were the first against a U.S. doctor for recklessly prescribing drugs, the Los Angeles district attorney's office said.

It's rare to bring homicide charges against a physician, but the case came amid a prescription drug abuse epidemic that has led lawmakers to try to rein in so-called pill mills that dole out medications with little scrutiny.

Dr. Hsiu Ying "Lisa" Tseng appeared in court during her arraignment in Los Angeles on March 16, 2012. AP

"You can't hide behind a white lab coat and commit crimes," Deputy District Attorney John Niedermann said. "Writing a prescription to someone knowing that they're going to abuse it and potentially die was the theory of second-degree murder that we had."

A dozen of Tseng's patients died, though prosecutors only brought three murder charges because of other factors involved in some of those deaths, such as drugs prescribed by other doctors and a possible suicide.

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Tseng, 45, showed no emotion as the convictions were read out loud, though her lawyer said she was emotional and very upset later. Jurors deliberated for 10 days before reaching the verdicts.

She was also convicted of illegally writing prescriptions for two of the deceased patients and 16 other people, including two undercover agents who were investigating how easily she prescribed addictive pain pills after brief office visits. She was acquitted of illegally writing a hydrocodone prescription to a third undercover officer.

Tseng prescribed "crazy, outrageous amounts of medication" to patients who didn't need the pills, Niedermann told jurors in Los Angeles County Superior Court during closing arguments.

The doctor repeatedly ignored warning signs even after several patients died as she built a new medical clinic in Rowland Heights with the money she made from them, earning $5 million in one three-year period. One patient even overdosed in her office and had to be revived.

"Something is wrong with what you're doing if your patients are dying," Niedermann said.

Tseng's lawyer said her client naively trusted her patients. Defense lawyer Tracy Green said patients testified they were legitimately in pain and later became dependent on the drugs, hiding their addictions by seeing other doctors and picking up prescriptions from different pharmacies.

Green had asked jurors to acquit Tseng on all but one drug count.

Tseng shouldn't have been convicted of anything more than manslaughter and plans to appeal, Green said after the verdict.

"It's disappointing," Green said. "I don't think it bodes well for doctors in America."

Tseng faces up to life in prison when sentenced Dec. 14.

She was convicted of killing Vu Nguyen, 29, of Lake Forest, Steven Ogle, 25, of Palm Desert, and Joseph Rovero, 21, an Arizona State University student from San Ramon. The three died of overdoses between March and December 2009.

Tseng barely kept any records on the three men until she was contacted by the Medical Board of California. She then fabricated charts to make it look like she kept thorough records of diagnoses and noted she was weaning them off drugs, Niedermann said.