James Barney Hubbard died by injection Thursday at Holman Prison near Atmore.
"The legal execution of James B. Hubbard was carried out according to the laws of the State of Alabama," Corrections Department spokesman Steve Hayes told CBS Radio News. "His official time of death is 6:36 p.m. Central Time."
Hubbard was executed for the 1977 murder of 62-year-old Lillian Montgomery of Tuscaloosa. She was shot in the head and robbed after befriending Hubbard, who had been released from prison after serving 19 years for a 1957 killing.
A pale, white-haired Hubbard maintained eye contact with his daughter Barbara McKinney, who witnessed the execution from another room, until he died.
Montgomery's son, Jimmy Montgomery, who also witnessed the execution, said he was disappointed that Hubbard offered no last words or apology.
"I didn't expect him to go as easy as he did today without saying something," Jimmy Montgomery said, adding that he did not forgive Hubbard and believed he deserved a harsher form of death.
Earlier Thursday, the Supreme Court voted 5-4 to deny a stay for Hubbard. His attorney contended the execution would amount to cruel and unusual punishment for someone so old and mentally incompetent.
Gov. Bob Riley rejected a request to commute Hubbard's sentence for what he called a "heinous and violent" crime.
"Justice has not been swift in this case, but justice must be delivered," Riley said.
According to the Coalition to Abolish the Death Penalty, Hubbard is the oldest person executed in the United States since 1941, when James Stephens of Colorado was executed at age 76.
In his filing with the Supreme Court, defense attorney Alan Rose said that although "Hubbard's age-based execution claim appears to raise a novel issue," it was in line with other claims of cruel and unusual punishment.
The state in arguing for the execution said that "murderers — especially repeat killers like Hubbard — do not deserve 'leniency' merely because their life of crime does not result in the imposition of a death sentence until later in life."
Hubbard, in his federal appeals, said he didn't speak up about his mental state and health sooner because the conditions didn't exist when he was younger. Court filings on his behalf say he has been diagnosed with dementia, along with other ailments.
Hubbard appealed to the Supreme Court Wednesday after a federal appeals court denied his request for a stay.
Chief Justice William Rehnquist and Justices Sandra Day O'Connor, Antonin Scalia, Anthony Kennedy and Clarence Thomas voted to deny the stay. Justices John Paul Stevens, David Souter, Ruth Bader Ginsburg and Stephen Breyer would have granted it.
State and federal authorities have executed more than 900 inmates since the U.S. Supreme Court ended the moratorium on the death penalty in 1976.