Jason Oric Williams is to be executed at 6 p.m. Thursday at Holman Prison in Atmore for the 1992 killing of four people during a shooting spree in Mobile County.
The 42-year-old Williams would become the first person to die in Alabama's death chamber using the drug pentobarbital.
Sodium thiopental was previously used in Alabama executions.
The state switched drugs because of a nationwide shortage of sodium
Williams has asked the 11th Circuit Court of Appeals to stop the execution.
He based his appeal on the state changing drugs and said there's no guarantee the new drug would not cause pain.
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