Ex-Oklahoma doctor pleads guilty to second-degree murder in 8 patients' drug overdose deaths

A former Oklahoma doctor has pleaded guilty to second-degree murder in connection to the drug overdose deaths of several patients.

William Valuck, a former pain management doctor, pleaded guilty Wednesday to eight counts of second-degree murder in Oklahoma County District Court.

Investigators have said Valuck prescribed more controlled narcotic drugs than any other physician in the state.

Valuck had originally faced eight counts of first-degree murder in connection with the deaths of patients who prosecutors say died of overdoses from drugs he prescribed them.

Federal and state authorities began investigating Valuck in February 2012, after being called by pharmacies and patients' relatives concerned about the amount of narcotics he was prescribing.

Authorities have said Valuck would prescribe as many as 600 pills at a time.