LOS ANGELES (CBSLA.com/AP) — Even after several patients died of overdoses, a California doctor charged in their deaths kept passing out prescriptions for powerful painkillers in appointments that lasted as little as three minutes, often without physical exams and despite red flags that she could be feeding addictions, a prosecutor told jurors Monday.

A defense attorney for Dr. Hsiu-Ying “Lisa” Tseng countered that some of those patients were suicidal, others were using the prescriptions to party, and all took well over the recommended dosage.

The lawyer painted Tseng as a somewhat naive doctor who was soft-hearted and never thought her patients would abuse her prescriptions.

“What the evidence is gonna show is that she tried to help these patients,” said Tracy Green, Tseng’s attorney. “She was acting like a doctor, not like a drug dealer.”

The conflicting portraits drawn in opening statements marked the beginning of Tseng’s murder trial, a rare charge for a doctor for prescribing drugs. Tseng, 45, could face up to life in prison if convicted.

Prosecutor John Niederman told jurors that a coroner notified Tseng of her first patient death by overdose in September 2007, two days after he had gotten prescriptions from her for oxycodone, Xanax, and Soma.

The next patient died six months later. Jurors were shown a picture of his body, lying face-down in his bed.

One patient overdosed in Tseng’s own clinic, Niederman said.

“The defendant was repeatedly notified by law enforcement that her patients were dying on her,” Niederman told jurors. “The evidence will show that during this period of time, the defendant’s practice of prescribing did not change at all.”

Niederman said jurors should find Tseng guilty of second-degree murder in the deaths of three of her patients, all young men. He said 12 of Tseng’s patients died in all, but only three were the subject of murder charges because other factors were involved in the other deaths.

Tseng’s attorney told jurors that her client, who came to the U.S. from Taiwan when she was 15, was a specialist in infectious diseases when her family convinced her to join her husband’s family practice because it was safer and she would be closer to home and her two children.

Tseng wasn’t trained in pain management and was trying her best to treat her patients, Green said.

“She was trying to help … She wasn’t callous or indifferent,” she said. “Lisa Tseng did not murder those three men.”

Green said the deaths were tragic but the case is “bigger than Lisa Tseng,” and other factors — the pharmacists who filled the prescriptions and drugs the men obtained from other doctors and on the street — also played roles.

“It’s difficult to place all of the responsibility on Lisa Tseng,” Green said.

The Drug Enforcement Administration says Tseng wrote more than 27,000 prescriptions over a three-year period starting in January 2007 — an average of 25 a day. She operated a storefront medical clinic with her husband in Rowland Heights.

The three murder charges stem from the overdose deaths of patients in 2009, including 21-year-old Joey Rovero, a senior at Arizona State University who grew up in the San Francisco Bay Area suburb of San Ramon.

His mother, April Rovero, says he was otherwise healthy and was set to graduate the year he died.

“These medications are extremely dangerous, extremely addictive. What happened to my son could happen to anybody’s child out there,” Rovero told CBS Los Angeles.

Rovero said her son never had any problems with addiction and once walked 2 miles home in the middle of the night after drinking beer with his buddies instead of driving.

“My son was a victim that needs to be represented,” she told The Associated Press. “When this happens to a child or a sibling, my experience is it changes your life irrevocably, forever. It’s not something you get over.”

Several civil lawsuits have already been filed and settled with Tseng. Larry Eisenberg represented eight families in the civil cases and was in court on Monday for opening statements.

“The evidence that was outlined in opening statement showed that she deposited $6 million into some 50 some-odd bank accounts over a number of years,” Eisenberg, a civil attorney, said.

Attorneys estimate Tseng’s trial will last between two to three months.

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