On Tuesday morning, the Georgia Board of Pardons and Paroles denied clemency for Troy Davis, clearing the way for the 42-year-old death row inmate’s execution by lethal injection at 7 p.m. this evening at the state prison in Jackson.

It is the fourth time in as many years that Troy Davis has faced execution. Barring a last-minute intervention by the US Supreme Court, which is highly unlikely, the state of Georgia will send a man to his death under conditions where the overwhelming preponderance of evidence points to his innocence.

The ruling has outraged Davis’s supporters, who gathered in demonstrations in Georgia and elsewhere Tuesday to protest the board’s decision. More than a million people have signed petitions demanding a halt to the execution, and the demand for clemency has been supported by a wide range of figures, including former president Jimmy Carter, the Pope and former FBI director William Sessions.

The prospect of executing an innocent man has provoked revulsion internationally. Bianca Jaggar, the Council of Europe’s ambassador on the death penalty, commented on the parole board’s decision, “To execute Troy Davis in these circumstances would be a travesty. Executing an innocent man is a state-sanctioned murder.”

The parole board ruling followed an all-day hearing on Monday, which took statements from Davis’s attorneys and witnesses in the morning, followed in the afternoon by prosecutors’ arguments and statements from family members of Mark MacPhail, the police officer Davis was convicted of killing.

Davis was convicted and sentenced to death in 1991 for the 1989 murder of MacPhail, who was moonlighting as a security guard at the time. MacPhail had intervened to stop the beating of a homeless man in a fast-food parking lot next to a bus station in Savannah, Georgia. There is no physical evidence connecting Davis to the crime and the murder weapon has never been recovered.

Since the trial, seven of nine witnesses for the prosecution at his 1991 trial have recanted their testimony, many stating that they testified falsely due to police intimidation. Several of these witnesses testified at Monday’s hearing, along with one of three jurors who voted to sentence Davis to death but have since come forward to say they would not do so now.

Brenda Forrest, one of the trial jurors, told the Georgia parole panel that while she had originally recommended the death penalty, she no longer stood by the verdict or the sentence. “I feel emphatically that Mr. Davis cannot be executed under these circumstances,” she said, according to the Atlanta Journal-Constitution.

Another defense witness at Monday’s hearing, Quianna Glover, testified that she heard Sylvester “Redd” Coles—the first person to identify Davis as the killer to the police and one of the two witnesses still supporting the prosecution’s version of events—confess that he killed McPhail. Numerous witnesses have sworn affidavits that it was in fact Coles who murdered McPhail.

The five-member Board of Pardons and Paroles dismissed the testimony of these defense witnesses and others, stating, “The Board has considered the totality of the information presented in this case and thoroughly deliberated on it, after which the decision was to deny clemency.” The panel did not provide a breakdown of board members’ votes.

After the decision was announced, Brian Kammer, one of Davis’s attorneys, stated, “I am utterly shocked and disappointed at the failure of our justice system at all levels to correct a miscarriage of justice.” At a press conference on Tuesday, Davis supporters said they were launching a last-ditch effort to halt the execution, calling on the Chatham County District Attorney to void Davis’s death warrant.

Troy Davis, who has always maintained his innocence, has spent 20 years on death row. The course of his case over these two decades has exposed a judicial system that operates in wanton disregard of basic legal and democratic rights.

As is now clear, the prosecution at Davis’s 1991 trial utilized testimony gained through police intimidation to push for his conviction and death sentence. Many of those who testified against Davis were threatened by the police that they would be tried as accomplices in the murder or be sent to jail if they did not name him as the triggerman.

During Davis’s state habeas proceedings from 1991 to 1996, when he was appealing his death sentence, he had no lawyer assigned to his case. This is because Georgia is one of a handful of states that does not provide indigent defendants with legal counsel for such proceedings.

The 1996 Antiterrorism and Effective Death Penalty Act (ATEDP), signed into law under Democrat Bill Clinton, has played a major role in preventing Davis from getting a new trial. The legislation imposes severe restrictions on the ability of death row inmates to seek relief in federal courts. Specifically, because Davis failed to obtain a hearing on his claims of innocence in Georgia courts, he could not get one at the federal level.

In August 2009, following a habeas corpus petition filed directly with the high court on Davis’s behalf, the US Supreme Court ordered a federal trial court to consider his case. The Supreme Court ordered the federal court “to receive testimony and make finding of fact” on whether new evidence could establish Davis’s innocence.

In June 2010, the federal district court in Savannah, Georgia met under Judge William Moore. The hearing heard several former accusers of Davis, who testified that they had been pressured by police to implicate Davis. While Moore ruled that the recantations “cast some additional, minimal doubt on his conviction,” he said the new evidence was insufficient to warrant a new trial.

The US Supreme Court in March of this year rejected without comment another appeal by Davis for a new trial. Tonight’s execution date was set earlier this month.

While 51 members of the US Congress have gone on record opposing the execution of Troy Davis, there has been no significant effort from politicians of either big business party to call a halt to it. Barack Obama has made no comment on the impending execution, and his press secretary has referred media questions about the case to the Justice Department.

Obama is an open supporter of the death penalty, writing in his memoir that while he thinks capital punishment “does little to deter crime,” he supports it in cases “so heinous, so beyond the pale, that the community is justified in expressing the full measure of its outrage by meting out the ultimate punishment.”

In recent years, the US Supreme Court has ruled that executions of the mentally impaired and those convicted of crimes as juveniles are unconstitutional, but it has done so to uphold the system of capital punishment overall, a barbaric practice outlawed by the vast majority of industrialized nations.

The blood of Troy Davis’s execution will be on the hands of the entire political establishment. They are implicated not only in his state killing, but in the deaths of the 1,267 individuals who have been executed since the Supreme Court reinstated the death penalty in 1976.