A doctor in California has been found guilty of murder for over-prescribing drugs that caused the fatal overdose of three patients, in a landmark verdict prosecutors called the first such conviction in the United States.

The case comes amid what public health officials describe as a national epidemic of prescription drug abuse.

The Centers for Disease Control and Prevention said last year the trend was fuelling nearly 17,000 overdose deaths annually, as well as arise in heroin addiction.

A Los Angeles County Superior Court jury deliberated nine days before convicting Dr Hsiu Ying "Lisa" Tseng, 45, an osteopath who specialised in internal medicine, of three counts of second-degree murder.

She also was found guilty of 19 counts of unlawfully prescribing controlled substance and one count of obtaining a controlled substance by fraud.             

Tseng, who has remained in custody since March 2012, faces a maximum penalty of life in prison when she returns to court on 14 December for sentencing, the Los Angeles County District Attorney's Office said.

Criminally prosecuting physicians for patients' deaths is relatively rare, with one notable case being the 2011 involuntary manslaughter conviction of Dr Conrad Murray for giving pop star Michael Jackson a fatal dose of a surgical anaesthetic to help him sleep.

Prosecutors last night said the verdict, capping a six-week trial, marked the first time in which a US doctor was found guilty of murder for over-prescribing drugs.

Licensed to practice in 1997, Tseng opened a storefront medical office in 2005 in Rowland Heights, a hillside community east of Los Angeles that is home to many upper-middle-class and wealthy immigrants from China, Taiwan and South Korea.

At the trial, prosecutors pointed to nine overdose deaths associated with Tseng's practice in less than three years, during which they said she had made $5 million from her clinic, dispensing potent, addictive medications to people who did not need them.

These drugs include powerful narcotics such as oxycodone, methadone and hydrocodone, and sedatives like Xanax and Valium.

She was convicted in the 2009 deaths of three patients – Vu Nguyen, 28, Steven Ogle, 24, and Joseph Rovero, 21.

None lived anywhere near Rowland Heights, and one, Mr Rovero, was an Arizona State University student from the San Francisco area.

Deputy District Attorney John Niedermann told jurors Tseng failed to keep records of patient visits or prescriptions in dozens of instances and faked medical records when authorities began investigating her.

Defence lawyer Tracy Green said patients put themselves in jeopardy by taking drug dosages "far in excess" of what Tseng had prescribed, according to an account of closing arguments by City News Service.

Tseng, who received her medical degree from Michigan State University, voluntarily surrendered her medical licence prior to arrest, but her federal licence to prescribe drugs was revoked.