The five-member Georgia Board of Pardons and Paroles will meet on Monday to consider whether to grant clemency to Troy Davis, a death row inmate scheduled to be executed on Sept. 21 for the 1989 murder of a Savannah police officer.

Troy Davis, 42, was sentenced to death 20 years ago for the murder of Savannah Police Officer Mark Allen MacPhail.

It's the fourth time in four years that the state has tried to execute Troy Davis, whose legal appeals are now exhausted.

Defense attorneys have told the media that the board can commute sentences and is Troy Davis' last hope.

The Georgia board is the only thing standing between Troy Davis and death. Back in 2008, the board had allowed his execution to go forward, but three new members have joined since then.

Troy Davis' execution is a rather controversial topic, as the defendant has maintained his innocence since being accused of the 1989 murder. That he has maintained his innocence throughout the years has attracted support from many to include former President Jimmy Carter and Pope Benedict XVI.

The case has also garnered worldwide attention with hundreds of public protest rallies held all over the globe opposing the judicial killing. Moreover, on Thursday, Troy Davis' supporters gave the paroles board the names of 663,000 people asking for him to be spared execution.

Advocates of the death row inmate who have been using social media to gather support to fight against his death has said Troy Davis is an innocent man. They have noted that several witnesses in the case have signed affidavits withdrawing their testimony, stating that police coerced them into accusing the 42 year old.

If I knew then what I know now, Brenda Davis, one of the jurors in the trial told CNN in a 2009 interview, Troy Davis would not be on Death Row. The verdict would be 'not guilty.'

Troy Davis' lawyers have argued for years that they can prove his innocence, and have managed to keep him alive ever since. But after a series of appeals receiving special attention from the U.S. Supreme Court, Troy Davis couldn't convince the courts to grant him a new trial, The Associated Press reported, and now they are back at the paroles board that is now considering whether to show him mercy.

Troy Davis was 19 when someone pointed him out as the man who killed Mark MacPhail, 27, was moonlighting as a security guard outside a Savannah bus station on Aug. 19.

According to The Atlanta Journal-Constitution, Mark MacPhail, a former Army Ranger with a wife and two young children, was moonlighting as a security guard when he heard the cries  of Larry Young, a homeless man who was being pistol-whipped in a Burger King parking lot early morning on Aug. 19, 1989.

Troy Davis was with a man name Sylvester Redd Coles, who was at the crime scene, and later allegedly said he was the real killer, when he began demanding Young to give him a beer.

But when Young refused, Troy Davis pulled out a handgun and began hitting Young with it, prosecutors said, according to the Journal-Constitution report. Mark MacPhail arrived on the scene and Troy Davis shot him, then stood over him and fired two more shots, prosecutors said. MacPhail never had a chance to draw his weapon.

During the murder trial, nine witnesses had testified that they saw Troy Davis at the scene, and saw him shoot Mark MacPhail or were told by the defendant that he killed the officer. However, since the trial, seven of those witnesses have either recanted or backed off their testimony, according to the Journal-Constitution.

Coles, who knew Troy Davis from the neighborhood and first pointed him out to police, hasn't changed his testimony, according to the Atlanta paper's report. Coles also told police that as he was leaving  the scene after Young was attacked, Mark MacPhail ran past him toward Troy Davis, and that's when he then heard a gunshot.

Coles has allegedly told family members and friends in recent years that he actually killed the off-duty officer, witnesses have said in sworn statements filed by the death row inmates' legal team, as reported by The Atlanta Journal-Constitution.

That report also noted that Quiana Glover of Savannah, has also said she was at a friend's house in June 2009 when Coles was there drinking heavilyand allegedly revealed he was the one who killed Mark MacPhail, Glover said.

It was definitely not the Troy we knew, Davis's younger sister Kim told The AP. It was very, very shocking when it did happen. It kind of turned the family upside down.

But the Davis family isn't the only one torn by the tragedy.

Mark MacPhail's mother Anneliese MacPhail told The AP that she is confident Troy Davis killed her son, and dismisses his advocates as ill-informed interlopers who have only prolonged her family's push for justice, according to The AP.

Anneliese MacPhail also said she's cautiously confident that will end Wednesday.

I think I finally will have peace of mind, said Anneliese MacPhail, who lives in Columbus. When it is over I can close that book and I know Mark can rest in peace, too.