BIRMINGHAM, Ala. (AP) — Authorities say a man has pleaded guilty to illegally selling a powerful painkiller that caused the death of a Birmingham-area woman.

Prosecutors say 31-year-old Rodrigus Lee Pearson of Birmingham pleaded guilty to distributing fentanyl that killed 20-year-old Ashlynn Bailey of Pelham.

Bailey was found dead of a drug overdose in a house in Birmingham on Jan. 30, 2016.

A statement from federal prosecutors says witnesses claimed Bailey had been buying heroin from Pearson. They say he probably substituted the fentanyl which was found in her system for heroin.

Fentanyl is a painkiller meant for cancer patients. It’s so strong it can kill in even tiny amounts.

Pearson will serve 20 years in prison under a plea agreement with prosecutors. Sentencing is scheduled for July 12.