Troy Davis, executed on his conviction for killing Police Officer Mark MacPhail, fought and maintained his innocence until his last breath.

Davis was still optimistic on the last day of his life because his death warrants had been stayed thrice since 2007, said Jason Ewart, a defense attorney who witnessed the execution.

I think he had high faith that he was going to be able to avoid this one, Ewart told Reuters.

On Thursday, Davis' attorneys described the Georgia inmate's last hours after 20 years in prison for a crime he always denied.

The night of the execution saw hundreds of people demonstrating outside the Georgia Diagnostic and Classification Prison in Jackson, where the execution was originally scheduled for 7 p.m. and then delayed for four hours while waiting for the final ruling from the U.S. Supreme Court.

Davis, who was 19 when the 27-year-old MacPhail was killed, told the slain police officer's relatives from the death chamber that he was innocent.

I am innocent. The incident that happened that night is not my fault. I did not have a gun. All I can ask ... is that you look deeper into this case so that you really can finally see the truth, the 42-year-old said, according to Sydney Morning Herald.

Davis last met with his family around 3 p.m. but then was allowed to talk to them on phone until around 6:40 p.m., said lawyer Danielle Garten, who acted as intermediary during the call, according to a Reuters report.

Davis had maintained a supportive relationship with his family despite being on death row and at the end of the final call they gathered round and yelled I love you into the phone, Garten said.

Davis made his final call to his lawyers.

Witnessing the execution in the death chamber were Davis' family, the MacPhail family, lawyers and journalists.

Ewart described the 15-minute execution as much more dramatic than he had expected.

He was on display and the whole thing was set up for the audience, and that's what disturbs me now. He was not on a flat gurney. It's a gurney that was tilted toward a giant picture window with a spotlight on him, he said.

The lethal injection was given at 10:53 p.m. and Davis was declared dead 15 minutes later, at 11:08 p.m., after the Supreme Court rejected an eleventh-hour request for a stay.

They filled him up with a paralytic and he was looking at me and I could see him go limp. I thought he was dead but then I saw him breathing. He could tell what was going on but couldn't move, he told Reuters.

The nurse walked up to him and opened his eyes and put the flashlight into them before a lethal shot was administered, Ewart added.

According to The Washington Post, AP reporter Greg Bluestein, one of five reporters to witness the execution, wrote that Davis gave a message to executioners just before he was given the lethal injection, saying: God have mercy on your souls.

Then, Davis blinked his eyes rapidly. He squeezed them tight. The curtain closed, Bluestein writes.

Davis asked his family and friends to continue to fight this fight after his death. He wanted his innocence to be proved to the world and his family to be proud, even if he is not physically present to see it, his lawyers said.

Demonstrators wept during a candlelight vigil outside the prison after Davis' execution.

MacPhail, who was off duty, was shot in the chest and face when he sought to intervene in an argument in a parking garage of a Savannah fast-food eatery and to rescue a homeless man.

The case became a death penalty cause because of the ambiguity of the evidence against Davis and the doubts expressed by many advocates over his guilt.

Seven out of the nine witnesses who stood against Davis, later recanted or changed their testimonies. Some of them said that they had been pressured by police to give their testimony, while some even said that there was another man who claimed to have shot MacPhail.

No gun, DNA evidence or surveillance footage was found to link Davis to the crime. Such incredibly flawed eyewitness testimony should never be the basis for an execution, Davis' attorney Stephen Marsh said. To execute someone under these circumstances would be unconscionable.