Bob Buchanan's son has spoken of his disbelief that his father was effectively set up to be murdered.
William Buchanan, a bank official in Northern Ireland, said today: "The findings are both incredible and shocking and confirm the existence of a mole in Dundalk station. This led to my father's death."
Superintendent Bob Buchanan, 55, was on his way back across the border with his colleague Chief Superintendent Harry Breen, 51 when they were ambushed by IRA gunmen in south Armagh.
Mr Buchanan was driving an unmarked Vauxhall and attempted to reverse his way out of the line of fire when the back wheels became stuck in a ditch.
But today's report confirmed they were victims of collusion.
William Buchanan said: "I know that a 'mole' theory has been in the background from the outset but this was very quickly discounted by the then chief constable of the RUC (Sir John Hermon) and the Garda commissioner at the time of the murders.
"The findings of Judge Smithwick are both incredible and shocking and confirm the existence of a mole in Dundalk station - this led to my father's death."
Mr Buchanan added: "I, on behalf of the Buchanan family, wish to place on record our appreciation for the diligence and integrity of Judge Peter Smithwick and his team. They have been untiring in the performance of their task and we trust the State will take cognisance of the findings and learn valuable lessons for the future."
Mr Buchanan was a recently married 25-year-old when his father was murdered. He recalled a phone call from a neighbour that he was needed at his parents' house and heard news reports about an ambush while driving home.
The policeman was described as a loving father and husband, hardworking and deeply religious. He wrote a book on his local church, Kellswater Reformed Presbyterian Church in Ballymena, which the family published after his death.
His lawyer also paid tribute to Judge Smithwick and revealed that he had initial doubts. Ernie Waterworth of the Belfast-based legal firm MTB (McCartan, Turkington, Breen), who attended virtually every one of the 132 days of evidence, said it had been a difficult process for the Buchanan family.
He said: "As a lawyer, I was at times sceptical as to whether there would be an open and honest finding, possibly due to a perception - very adequately described by Judge Smithwick - that in the south of Ireland there existed a culture of failing adequately to address suggestions of wrongdoing, either by political expedience or by virtue of misguided loyalty, that has been a feature of life in this state.
"Judge Smithwick and his team deserve credit in what was a very trying and difficult process. They remained determined to complete their inquiry, despite all of the setbacks and obstacles which confronted them.
"To present the findings as they have is reassuring. Judge Smithwick highlights his desire for the State to move away from this culture of ignoring wrongdoing and to embrace an open and honest approach in all matters, irrespective of the consequences. We now await with interest how the State responds to the findings and recommendations of Judge Smithwick."