San Francisco-based Dr Hootan Roozrokh, who could face up to eight years in jail if convicted, denies the charges.

He is accused of ordering large amounts of narcotic painkillers and sedatives for a Ruben Navarro, 25, before he was officially declared dead.

Mr Navarro's mother says her son was exploited and did not die with dignity.

Dr Roozrokh is also charged with administering the antiseptic Betadine through a feeding tube into the patient's stomach. That procedure typically takes place once a donor has died.

Prosecutors claim this occurred just after Mr Navarro, who was physically and mentally disabled, was taken off life support. He survived for another seven hours.

The BBC's David Willis, in California, says that with nearly 100,000 people on the national waiting list for organs, the case has raised questions about the ethics of removing a patient from life support simply to retrieve their organs.

He adds that some believe the charges against Dr Roozrokh could prompt surgeons to be more cautious in how and when they recover organs.