The 64-year-old doctor, Dewey C. MacKay III, showed up Tuesday at Federal Correctional Institution in Terminal Island, Calif., a prison near the Los Angeles Harbor.
A jury convicted MacKay in September of illegally distributing painkillers. Authorities say he saw 80 to 120 patients a day and dispensed millions of pills over the years.
MacKay also was convicted in a drug overdose death. One of his patients, a 55-year-old rocket scientist, died three days after filling prescriptions from MacKay in 2006.
Prosecutors say MacKay was supposed to show up Monday but a sealed court order gave him an extra day to arrive at the prison.
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