A doctor is on trial on manslaughter charges after New York City authorities said he sold painkiller prescriptions to two patients who died of overdoses.

Opening statements began Wednesday in Dr. Stan Li's (leez) case. A narcotics prosecutor portrayed him as a drug dealer with a medical degree.

Prosecutors say Li kept writing narcotics prescriptions to one patient who overdosed five times in a year and another whose father implored him to stop.

Another patient shot and killed four people in a pharmacy holdup.

Li's lawyer says the New Jersey-based doctor acted properly. The defense says he didn't know some patients were misusing drugs he prescribed.

Authorities around the country have used civil and sometimes criminal laws to pursue doctors suspected of peddling prescriptions. But manslaughter charges are rare.