Despite spending the last 22 years striving to prove his innocence, death row prisoner Troy Davis has been executed.

The 42-year old lost his lengthy legal battle – one of the most disputed cases in American legal history – late last night and was executed in Georgia State Prison, Jackson.

He was given a lethal injection half an hour after the US Supreme Court rejected his last-ditch attempt at appeal, but insisted his innocence until he died.

Davis was accused of the death of 27-year-old police officer Mark MacPhail in 1989.

Before he died, he told the victim’s family: "I was not responsible for what happened that night. I did not have a gun. I was not the one who took the life of your father, son, brother. I am innocent."

MacPhail’s son and brother watched in silence as he continued: “All I can ask…is that you look deeper into this case so that you really can finally see the truth.”

He pleaded for family and friends to “continue to fight this fight”.

Then he said to prison officials: "For those about to take my life, may God have mercy on your souls. May God bless your souls."

Davis’ lawyer Thomas Rufifn said it was “a legalised lynching” and described the injection – which killed Davis in moments – as “sickening”.

He said: “I saw the tube inserted into his arm, and then fluid, then jerking. It's sickening. It's worse than any film adaptation. It's more macabre and horrible than anything on film and television.”

Troy Davis denied lie detector test hours before execution

There was no physical evidence, blood samples or DNA linking Davis to the crime and several members of the jury came forward to say they’d given the wrong verdict.

The case was based on nine witness statements, but seven of those said that police officers had coerced them into delivering it. Another witness claims that another man, Sylvester Coles, confessed to the murder in private.

However MacPhail’s family believe that justice has finally been done.

His mother, Anneliese MacPhail dismissed Davis’ claims of innocence and said: “All the feelings of relief and peace I've been waiting for all these years, they will come later. I certainly do want some peace.”

Outside the prison over 500 demonstrators cried, hugged, prayed and lit candles, next to more than 100 Georgia state troopers in riot gear.

A rally was held in Paris with over 150 demonstrators carrying signs emblazoned with Davis’ face.

Davis’ supporters included former President Jimmy Carter, Pope Benedict XVI, a former FBI director, the National Association for the Advancement of Coloured People (NAACP) and celebrities like Big Boi from Outkast and hip-hop star P Diddy.