William Stobie, who was shot dead outside his home in northwest Belfast early yesterday morning, was recruited by the RUC Special Branch as an informer after he was questioned about the murder of a young Protestant man in November 1987.
That victim was Mr Adam Lambert, a 19-year-old builder from Co Tyrone. He was shot dead by the Ulster Defence Association (UDA) the day after the Enniskillen bombing by the IRA, which killed 11 Protestants at the town's Cenotaph on Remembrance Sunday. The UDA had intended to kill a young Catholic on the building site where Mr Lambert worked. His death was a case of mistaken identity.
Stobie was a senior member of the UDA in the Forthriver area where he lived, holding the rank of quartermaster, and was involved in supplying the gun used in Mr Lambert's murder. He was never charged but began to work as an informant, passing information about the UDA's activities including plans to kill people.
Just over a year after he was recruited he said he told the RUC about UDA plans to kill "a Catholic". The intended victim, it turned out, was the Catholic solicitor Mr Pat Finucane, who was then the head of one of the most effective criminal defence legal companies in Northern Ireland.
Mr Finucane primarily represented members of the Provisional IRA and his successes in court and his representation of families of republicans shot dead by the RUC had made him a prominent figure. He was also the solicitor chosen by the IRA leadership to represent the interests of the IRA prisoners on hunger strike in the Maze Prison in 1981. He was, therefore, a highly visible target for loyalists.
The murder of such a public figure immediately led to controversy. Shortly before his death a British government minister referred in the House of Commons to legal figures in Northern Ireland who were unduly sympathetic to the IRA. This was taken as a clear reference to Mr Finucane.
Earlier in his career Mr Finucane was questioned by the RUC after eight IRA men escaped from Crumlin Road Prison. The RUC may have suspected at the time that the handguns used in the breakout had been smuggled to the men by Mr Finucane who had visited some of his clients in the prison shortly beforehand. This claim was never substantiated.
An inquiry into the circumstances surrounding Mr Finucane's murder was set up under the Deputy Commissioner of the Metropolitan Police Force, Mr John Stevens. This inquiry led to Stobie's door. He was charged with aiding and abetting the murder of Mr Finucane in January 1999.
The case against Stobie came to court this autumn but collapsed last month when the key witness, former journalist Mr Neill Mulholland, who had interviewed Stobie about the Finucane and other murders, was unable to give evidence.
Mr Mulholland, who had left journalism and was working as a press officer at the Northern Ireland Office, has been under intense personal pressure since it was revealed by other journalists that he had information linking Stobie to the Finucane death. Counsel for the Director of Public Prosecutions in Belfast told the trial there was clear evidence that Mr Mulholland was not in a fit state to give evidence. The charges against Stobie were withdrawn.
With Stobie's murder, it is now even more unlikely that the full truth of the events surrounding Mr Finucane's murder will come into the open.
Another key UDA figure who knew the circumstances surrounding the Finucane murder died six years ago. Tommy Lyttle was the UDA commander in west Belfast at the time and is believed to have directed the Finucane murder.
During the Stevens Inquiry into collusion between the security forces in Northern Ireland and the loyalist terrorist groups, Lyttle's fingerprint was found on documents containing details of suspected IRA members.
There were strong suspicions among UDA members that Lyttle was also acting as an informant for either the RUC Special Branch or the British army.
It had emerged long before the Stevens Inquiry that British army intelligence staff was in the habit of passing these documents to the UDA in a public house in west Belfast.
The intention, it seems, was to provide the loyalists with assistance in targeting and attacking IRA figures who might be expected to be preparing attacks on the army or RUC.
The Stevens investigators found huge amounts of these documents and also discovered that the British army had planted an agent, Brian Nelson, in the Belfast UDA and gave him exclusive access to the information on IRA suspects.
Nelson was arrested in 1990 and charged with involvement in five murders and sentenced to 10 years imprisonment. After his release he was given a new identity and his whereabouts since have remained a secret.
Had Nelson not been secreted out of Northern Ireland and had Tommy Lyttle not died of a heart attack in 1996, it is likely they would have become UDA targets.
It seems Stobie somehow believed the publicity surrounding his case might excuse him from the type of summary execution meted out by the terrorist groups to informers in Northern Ireland.
In some ways his case is remarkably similar to that of Eamon Collins, the former south Armagh IRA man who turned informant and then wrote a book about his activities in the IRA, which included the names of many of its leading figures. He was killed by the IRA near his home in Newry in January 1999.