Kevin Crilly was cleared at Belfast Crown Court today of murdering undercover soldier Captain Robert Nairac 33 years ago.
Crilly, 60, from South Armagh, Northern Ireland, had denied murdering the Grenadier Guardsman in May 1977.
In one of the most infamous killings of the Troubles, Captain Nairac was abducted from a bar in Drumintee near the border with the Irish Republic before being shot dead.
Mr Justice Richard McLaughlin said: "The prosecution has not proved beyond reasonable doubt the state of knowledge or intention necessary to transform the transporting of (Liam) Townson (who was convicted of the murder) by Crilly to an unspecified place at an unspecified time into a knowing participation in a potential murder. For these reasons I find the accused not guilty."
He was cleared on all five charges which he faced, including kidnapping and false imprisonment as well as murder after he was accused of dropping off the killer.
Following the murder, Crilly, from Lower Foughill Road, Jonesborough, went to the US for 27 years, using his birth name, Declan Power.
The prosecution claimed that, following the kidnapping of Capt Nairac from the Three Steps Inn, Crilly, then 26, picked up the gunman, Liam Townson, who was later convicted by the Special Criminal Court in Dublin.
Crilly was asked about the killing by BBC Spotlight journalists.
The judge said: "The admissions by Crilly to the journalists from the Spotlight programme prove he was involved to some degree in the events surrounding the death of Captain Nairac.
"He was present at the Three Steps Inn where what he described as a 'battle' took place. This can only mean what he witnessed was the abduction of Captain Nairac but it does not prove his active participation in it."
He said the evidence did not prove where Capt Nairac was at the time Crilly went to collect Townson or when he dropped him off, nor does the evidence establish when or by whom the decision was made to kill him.
"I have concluded that the prosecution has not proved Crilly was a participant in the abduction," the judge added.
A fearless maverick who played by his own rules, Captain Robert Nairac finally ran out of luck when he strode into a bar in an IRA heartland and broke into song.
The undercover soldier, who read spy novels as a child, told republicans in Drumintee's Three Steps Inn he was Danny, a comrade from Belfast.
As the night wore on and drinks flowed, the Grenadier Guardsman took to the stage and treated punters in the South Armagh watering hole to the rebel ballad Broad Black Brimmer.
They clapped and he sang again, and again.
Alone and without backup, the Oxford boxing blue, an assumed Belfast brogue replacing his clipped English accent, was trying to establish his republican credentials and win the confidence of the local IRA unit.
But for this soldier, one seemingly addicted to danger, it proved a risk too far.
Assaulted as he tried to leave, bundled into the back of a car and driven across the Irish border, the 29-year-old's last hours would be spent in agony as his attackers tried in vain to make him come clean.
Punched, kicked, pistol-whipped and beaten with a fence post, still he refused to talk.
At one point in the interrogation, an IRA man arrived dressed as a priest and tried to dupe the devout Catholic into confiding. It did not work.
Exasperated, his captors turned executioners and killed the unbroken captain with a bullet to the head.
His body has never been found amid rumours it was minced at a meat processing plant.
Two years later, he was posthumously awarded the George Cross, his citation hailing him a hero.
It read: "Captain Nairac's exceptional courage and acts of the greatest heroism in circumstances of extreme peril showed devotion to duty and personal courage second to none."
While his bravery has never been questioned, the soldier's legacy is not without taint.
Some former colleagues paint him as a brave but reckless officer, whose romantic view of soldiering led to him losing his life.
He was not in the SAS and, as a liaison officer in an undercover unit, there are those who have questioned if he even had the authority to engage in such audacious intelligence operations.
"Robert certainly stuck his neck out. He thought he could get away with it, but in a way we all do," his sister Gabrielle is quoted as saying.
"As a small boy, he had read Bulldog Drummond, so you can imagine his approach."
But the captain has also been linked to much graver allegations.
Republicans have claimed the undercover operative had been providing information that military intelligence used to assist loyalist paramilitary groups who carried out a string of murders in the South Armagh area.
There are also allegations of involvement in the loyalist bombings of Dublin and Monaghan in 1974 and in the murders of members of the Miami Showband in 1975.
No evidence of collusion has been proved against him.
Capt Nairac was born in Mauritius and had a privileged upbringing, being sent to private prep school, leading Catholic public school Ampleforth College and then on to Lincoln College, Oxford, where he read medieval and military history and excelled in sport.
A talented rugby player, he turned out for Oxford's 2nd XV and also boxed for the university, winning four blues in bouts against Cambridge.
Legend has it that prior to the troubles, Nairac encountered future IRA godfather Martin Meehan in the ring in an amateur contest in England.
After university he entered the Royal Military Academy Sandhurst under the sponsorship of the Grenadier Guards and took a commission in the regiment on leaving.
His first tour of duty in Northern Ireland came in 1973 when he spent three months with the Second Battalion of the Grenadier Guards in Belfast.
At the end of his tour of duty he remained for a time as liaison officer with the replacement battalion.
When his regiment was posted to Hong Kong, he volunteered for intelligence duties in Northern Ireland instead and returned in 1974.
Ultimately, that love for Ireland, fostered on holidays to Dublin and Co Galway as a child, was to cost him his life.