Troy Davis’ execution will go ahead as planned.

Troy Davis case story. Last day before execution.

Troy Davis, the convicted murderer of a police officer, who is set to be executed by lethal injection on Wednesday, has lost a bid for clemency launched by his defense lawyers.

Georgia’s board of pardons rejected the last-minute plea even after it attracted high-profile support, and Troy Davis execution will go ahead as planned.

It was the last hope for Troy Davis, 42, who was convicted of killing police officer Mark MacPhail, in Savannah, Georgia, in 1989.

Anti-death penalty activists, who claim Troy Davis was wrongly convicted, chanted and held banners through Atlanta last week.

It is the fourth time in four years Troy Davis execution has been scheduled by Georgia officials.

According to Steve Hayes, spokesman for the Board of Pardons and Paroles, the panel decided to rejected Troy Davis’ request for clemency after hearing hours of testimony from his supporters and prosecutors.

The board decision appeared to leave him with little chance of avoiding the execution date. Defence attorney Jason Ewart has said that the pardons board was likely Troy Davis’ last option.

The defense lawyers have long argued Troy Davis was a victim of mistaken identity, but prosecutors say they have no doubt that they charged the right person with the crime.

Officer Mark MacPhail’s relatives said they were relieved by the decision.

“That’s what we wanted, and that’s what we got,” said Anneliese MacPhail, the victim’s mother.

“We wanted to get it over with, and for him to get his punishment.”

“Justice was finally served for my father,” said Mark MacPhail Jr, victim’ son, who was an infant when his father was gunned down.

“The truth was finally heard.”

Troy Davis’ sister, Kim Davis declined immediate comment on the decision.

Amnesty International USA director Larry Cox said in a statement that the decision was “unconscionable”.

“Should Troy Davis be executed, Georgia may well have executed an innocent man and in so doing discredited the justice system,” Larry Cox said.

The case has captured international attention because of concerns about the quality of evidence involved in Troy Davis’s conviction.

Troy Davis’s supporters said there is no physical evidence linking him to the crime and that key witnesses in his trial have since recanted their testimony.

Martin Luther King III, son of the late civil rights leader Martin Luther King Jr, joined the last week march. Reverend Al Sharpton, a civil rights activist and television show host, also attended.

In August 2009, in a rare move, the U.S. Supreme Court ordered a new hearing for Troy Davis to assess what he said was new evidence showing his innocence.

The justices transferred the case to a U.S. District Court in Georgia for a hearing and determination of Troy Davis claims that new witnesses will clearly establish his innocence.

In 2010, the judge, William T. Moore Jr, rejected Troy Davis’ claims of innocence. But last week, supporters of Troy Davis delivered petitions with more than 600,000 names to the parole board.

In a column last week in the Atlanta Journal Constitution, former FBI Director William Sessions called for Troy Davis’s sentence to be commuted to life in prison, saying the case was “permeated in doubt”.

However, in an opposing column written in late 2008 and republished on last Thursday, Spencer Lawton, the district attorney who prosecuted Davis, said the convicted man had a fair trial.