Dr. Kachun C. Yeung pleaded guilty to two counts of prescribing the powerful painkiller Oxycodone "outside the course of professional medical practice and not for a legitimate medical purpose."

Also known as OxyContin and "hillbilly heroin," the drug is addictive and has been widely abused.

According to papers filed by federal prosecutors in the case, the investigation of Yeung, 53, began after 11 patients who were being prescribed medications by him died of drug overdoses here between August 2000 and August 2002. The government never alleged that Yeung had any responsibility in those deaths, but filed the paperwork to refute allegations from Yeung's attorney that drug agents were unfairly targeting physicians specializing in "pain management."

The investigation was carried out by undercover agents of the U.S. Drug Enforcement Administration posing as patients of Yeung.

Last year, Yeung's son, University of Hawai'i student Christopher Yeung, posted photographs of DEA agents on WhosaRat.com, dedicated to identifying law enforcement informants and undercover agents.

Christopher Yeung, who was a paralegal assisting in the father's case, obtained the images from government surveillance tapes turned over to criminal lawyers defending his father.