Quotes of the Day

To Irish Republican Army members, they are known as the "security department." Everyone else calls them the "nutting squad" for their habit of putting bullets into people's heads (or "nuts," as they're called in Belfast). By whatever name, this I.R.A. group — charged with maintaining internal security — is feared for its brutality, ruthlessness and familiarity with remote parts of the Irish borderland, where those deemed guilty of passing information to the British are routinely found after nutting. So people on both sides of Northern Ireland's Catholic-Protestant divide were shocked last week to learn that the nutting squad's deputy commander may have been a British agent codenamed Stakeknife — and that he may have participated in murder to protect his cover.

The Stakeknife legend has been circulating in British newspapers since 1999, when intermittent reports began appearing suggesting that an uber-agent was at work at the heart of the I.R.A., handing the British Army vast amounts of information about the group's attacks and membership. Stakeknife's reports were said to be so detailed that the British needed a dedicated team of experts to sift through all the facts. Republicans always dismissed the rumors as an elaborate intelligence bluff designed to set the I.R.A. off on a self-destructive witch hunt. And even if a mole did exist, republicans thought it inconceivable that he could operate for decades without giving himself away to the nutting squad. Now British police say Stakeknife does exist, and some disgruntled republicans are starting to believe his information helped steer the I.R.A. into the current peace process.

The Stakeknife story resurfaced last week when the British and Irish media, quoting unnamed security sources, identified Stakeknife as Alfredo (or Freddy) Scappaticci, an Italian immigrant's son who was previously known only as a low-profile republican. Once the story broke, Britain's Ministry of Defence confirmed the existence of the agent, but declined to name him. Scappaticci, a burly builder, promptly disappeared from his West Belfast home. Three days after he was accused, Scappaticci re-emerged — still in West Belfast — to deny being Stakeknife. "I am telling you I am not guilty of any of these allegations," he said. "Nobody had the decency to ask me if any of these allegations were true."

Scappaticci admitted he was a republican, but said he cut his ties to the I.R.A. in 1990 — the same year he was accused, but not convicted, of being a nutting squad interrogator. British sources say he is brazening it out; republicans aren't so sure. There is enough in his background to make them suspicious, but they are equally wary of being duped when the British are so willing to own up to Stakeknife's existence.

The Stakeknife story is all the more dramatic because of allegations by a former British Army spymaster, known by the pseudonym Martin Ingram, that the agent ordered and participated in "multiple" nutting squad murders of other informers to protect his own identity. Simply by joining illegal paramilitary groups, the hundreds of informers who worked for the British were breaking the law. But Stakeknife and others — in both the I.R.A. and loyalist groups — are believed to have taken that license further and killed, either to confirm their terrorist credentials or advance other interests, like drug dealing. "You never dreamed that was going to happen," says Raymond McCord, who discovered that a police agent was suspected of killing his son. "That someone has been allowed to kill and kill and kill simply because they worked for the British government."

After Scappaticci broke cover, Sinn Fein leader Gerry Adams said the episode showed "the British Government and its agencies were up to their elbows in killing and in destroying people's lives." Privately, though, republicans are assessing how much the I.R.A. may have been compromised. Under pressure to disband, it could find its internal resolve sapped by the disturbing suggestion that a British agent helped shepherd them into a ceasefire.

For the British, the fallout could be equally, if not more, serious. A lengthy investigation by John Stevens, Britain's most senior cop, has already demonstrated that British security agents were directly involved in the 1989 murder of Pat Finucane, a Belfast lawyer. Stevens now wants to interview Stakeknife, and other investigations loom — such as the one into British involvement in the 1974 loyalist bomb attacks in Dublin and Monaghan that killed 32 people. Last week's revelations fit a pattern Stevens found in the way British agents operated — there were no rules and they were above the law. The British will find it hard to push for a clean I.R.A. break from the past if their own heinous crimes continue to bob to the surface.

• CHRIS THORNTON | Belfast
• Did an I.R.A. informant kill repeatedly to safeguard his identity?