The man could be the oldest person put to death in the modern era of US capital punishment.
Alabama is set on Thursday to execute an 83-year-old convicted pipe-bomb killer who could be the oldest person put to death in the modern era of US capital punishment.
The execution of Walter Moody is planned for 6 p.m. (2300 GMT) at the William C. Holman Correctional Facility in Atmore. It would be the eighth this year in the United States.
If the execution is carried out, Moody would replace John Nixon, who was 77 when put to death in December 2005 in Mississippi, as the oldest person executed since the US Supreme Court reinstated the death penalty in 1976, according to the Death Penalty Information Centre, which monitors US capital punishment.
Moody was convicted of mailing a bomb in 1989 that killed US Circuit Court Judge Robert Vance, 58, and another that killed Georgia civil rights attorney Robert Robinson.
Prosecutors have said Moody sent the bomb to the judge in anger over a 1972 bomb conviction that Moody felt derailed his career and sent another to the civil rights lawyer to confuse investigators.
Moody, who has spent more than 20 years on death row, has maintained his innocence and his lawyers have not yet used his age in appeals seeking to halt the execution. He has applied for clemency at the state level. As of Wednesday afternoon, there were no appeals registered in the federal court system, online records showed.
Age and poor health were major factors in a botched execution in Alabama earlier this year when the state tried to put to death Doyle Hamm, 61, who had terminal cancer and severely compromised veins.
The execution was called off while Hamm was on a death chamber gurney and medical staff could not place a line for the lethal injection.
Lawyers for Hamm called on the state not to try to execute him again and reached a settlement with Alabama in March that a legal source said would keep him out of the death chamber.