Three investigations
Sir John Stevens, then a senior English police officer, was first brought to Northern Ireland in September 1989 to look into leaks of security force documents to loyalist paramilitaries. That first investigation, Stevens I, led to the arrest of Brian Nelson and the discovery that he was an Army agent. A second investigation followed in the 1990s. The third, Stevens III, began in 1999 and looked specifically at the Finucane murder and the killing of Brian Adam Lambert in 1987.
The 2003 overview
On 17 April 2003 Stevens published an overview and recommendations from his third investigation. The full report was not published. In the overview he concluded that there had been collusion in both murders, and he listed failings that included the withholding of intelligence and evidence, a failure to keep records and an absence of accountability. He also described obstruction of his investigations over many years.
The overview made recommendations about agent handling and record-keeping. When the government responded to the de Silva report in 2012, the Prime Minister pointed to reforms made since 1989, including the statutory framework for informants in the Regulation of Investigatory Powers Act 2000.
How the later reports used it
Sir Desmond de Silva had full access to the Stevens archives for his 2012 review and describes them in chapter 1 of his report. He examined the obstruction of the first Stevens investigation in chapter 24, finding that the Army and RUC Special Branch deliberately obstructed it. The Director of Public Prosecutions for Northern Ireland decided in 2007 that no members of the security forces would be prosecuted on the basis of the Stevens III files.