JACKSON -- Georgia death row inmate Troy Anthony Davis, who faces lethal injection Tuesday for the 1989 murder of a Savannah police officer, prayed with New York civil rights activist Al Sharpton, the latest well-known figure appealing to spare his life.

Sharpton said Davis, 39, was "surprisingly upbeat" Saturday night after the two prayed together at the Jackson prison. Davis has claimed he is innocent in the shooting death of officer Mark Allen MacPhail, who was killed on Aug. 19, 1989.

Sharpton spent about 35 minutes with Davis, and said by phone that the death-row inmate reflected on how he became a murder suspect.

"He said he got in with the wrong crowd and thought one of the guys he was hanging with killed" MacPhail, Sharpton said. "He said young people should be careful who they hang around."

Pardons and Parole Board spokeswoman Scheree Lipscomb said she does not expect any last-minute clemency for Davis, whose supporters include former President Jimmy Carter. The former president asked the board Friday for a stay of execution.

The slain officer's mother, Anneliese MacPhail, 74, of Columbus, said she is "disgusted" by the outpouring of support for Davis and said she had no doubt Davis is guilty.

"I hope this is over Tuesday and I can have some peace," she told The Atlanta Journal-Constitution for a story Sunday.

She said three of her children will attend the execution. She will not.

A rally for Davis by Georgians for Alternatives to the Death Penalty and the NAACP is planned Monday in front of the State Capitol.

Since Davis' 1991 trial, several key witnesses have recanted their testimony.

Witness testimony formed the core of the prosecution's case because physical evidence was scant: no murder weapon, no fingerprints, no DNA.

In a statement Friday, Carter said he asked the parole board to reconsider the case, saying it "illustrates the deep flaws in the application of the death penalty in this country."

Carter wrote that "executing Troy Davis without a real examination of potentially exonerating evidence risks taking the life of an innocent man and would be a grave miscarriage of justice."

The case has attracted worldwide attention, with calls to stop his execution from Pope Benedict XVI, Amnesty International and Nobel Peace Prize-winner Desmond Tutu. Rallies have been held as far away as Paris.