LONDON -- Gerry Adams, the leader of the Northern Irish political party Sinn Fein, was released from police custody without charges Sunday after four days of questioning into a gruesome 1972 Irish Republican Army murder of a widow with 10 children.
But the police will hand over a file of potential evidence against him to British prosecutors, police officials in Northern Ireland said.
Mr. Adams, 65, turned himself in for questioning Wednesday in Antrim and was arrested; his detention was extended for 48 hours by a judge after a police application. He was released shortly before 6 p.m. local time from the police station in Antrim, escorted from a back entrance to avoid a small crowd of protesters.
The police are working on allegations made in the testimonies of IRA dissidents, now dead, that were handed over under subpoena by Boston College, which had collected them.
Mr. Adams has been accused over the years of membership in the IRA and of being the group's commander in Belfast, Northern Ireland. In these testimonies, he was accused of having ordered the abduction, murder and secret burial in 1972 of the widow, Jean McConville, who was suspected of being an informer for the British army. Her body was found only in 2003, and the police considered hers a cold case until the testimonies emerged.
Mr. Adams denies all the accusations. And though he has long been the leader of Sinn Fein, once the IRA's political wing and now a prominent political party, he has never admitted to membership in the IRA, unlike his deputy, Martin McGuinness.
Prosecutors could choose to prosecute Mr. Adams later, even just on a charge of being an IRA member. But that charge alone after so many years would be widely seen by Sinn Fein and its allies as political interference.
Mr. Adams, a former member of the British Parliament from West Belfast and a current member of the Irish Parliament, the Dail, from County Louth, has led Sinn Fein since 1983. The party is running well in the Irish Republic ahead of elections this month for local councils and for the European Parliament.
In a Belfast news conference Sunday evening, Mr. Adams said he was innocent and committed to a peaceful future for Ireland, north and south. "There is no going back," he said. "The IRA is gone. It's finished."
The police timing was poor, Mr. Adams said, given the election campaign. "Those that authorized this didn't make the right strategic decision," he said. "This is entirely a wrong signal" about evenhanded policing. But he said he supported the police.
The police and officials from Britain, Northern Ireland and Ireland have all rejected accusations from Sinn Fein and Mr. McGuinness that the arrest of Mr. Adams was political in nature and stemmed from a "dark side" of the current Police Service of Northern Ireland.
But the arrest has unsurprisingly produced tension within the power-sharing government of Northern Ireland. The first minister, Peter Robinson, of the Democratic Unionist Party, speaking of "republican bullyboy tactics," accused Sinn Fein of trying to blackmail the police.