Thirty-three-year-old Jerry Bryant was found guilty in the January 1997 kidnapping and shooting death of another man.
The body of 27-year-old Donald Hollis was found off a dirt road in Florida, but prosecutors said he was abducted and killed in Dothan.
The same jury that convicted Bryant also voted 11-1 for the death penalty.
But the State Supreme Court has ruled those jurors were not properly instructed before they deliberated.
Bryant's conviction will stand but a new jury will have to be picked for re-sentencing and Bryant could get life without parole.
A hearing date has not been set.