Gerry Adams faces questioning by detectives if a federal court in Boston rules that transcripts of interviews with seven former IRA members about the murder of widowed mother-of-10 Jean McConville can be released to the Police Service of Northern Ireland.
Mrs McConville's family is also exploring the possibility of launching a civil action against the Sinn Fein president in the event of no prosecution taking place.
Mr Adams maintains he had "no hand, act or part in" the December 1972 murder, despite claims by two of his former IRA associates, Dolours Price and Brendan Hughes, that he gave the order for the killing and secret burial (in Co Louth) of the Protestant woman who had been living in the Catholic Falls Road area.
Fianna Fail leader Micheal Martin told Mr Adams in the Dail last week that it is time to "come out of the shadows" on the issue of his past relationship with the IRA.
"Far from the passage of time erasing memories of these issues, they are instead becoming clearer and more relevant," he said, referring to the escalating controversy over Boston College tapes allegedly linking the Sinn Fein leader to the death of Mrs McConville.
Mr Martin spoke of the murder by the IRA of the woman struggling to bring up her children.
"Brendan Hughes, who was a key member of the Belfast brigade of the IRA at the time, pulls no punches in his claims of who ordered that killing," he said. "It is a very sordid tale. Deputy Adams owes it to the House to make a comment on it."
Mr Martin said he has written to Hillary Clinton on the issue, and will be asking the Taoiseach "whether he sees the need to discuss the pursuit of this by the PSNI and the British authorities with the American authorities".
The concerns of the opposition leader provoked a sharp response from Mr Adams, who claimed that "the IRA, which is now on ceasefire, has left the stage and is not around, apologised for what it did" and added that "those who make the accusation against me, apart from those in the Dail, are implacable opponents of the peace process".
Mr Adams's denials, said Mr Martin, "fundamentally lack credibility, and were it any other politician who stood accused of what Mr Adams is, they would be facing, at a minimum, a Dail inquiry or a commission of inquiry".
Brendan Hughes died in 2008 and Dolours Price took her own life last January at her home in Malahide, Co Dublin. Both had given accounts to researchers for Boston College stating that Mr Adams had given the order for Mrs McConville's murder in his role as head of an IRA unit in Belfast whose job was to seek out and punish anyone seen as collaborating with the British Army or the RUC.
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Last Friday week, the PSNI took possession of the Dolours Price transcript, which had been in the possession of the US Department of Justice since last year. It and the tapes – part of a Boston College collection of recordings of former republicans and loyalists – is unlikely to lead to any action being taken against Mr Adams as Price had known mental health issues.
However, a federal court in Boston is expected to give final judgement next month in the appeal by Boston College in relation to 11 interviews with seven former IRA members also relating to the McConville murder and which are still held by the college.
In April, the Federal Appeals Court ordered that these tapes be handed over to the Department of Justice by the end of this month. Boston College is still considering this order but, if as appears likely it is compelled to release the tapes, the PSNI would then have no option but to question the former IRA members and Mr Adams.
Boston College said last week that reports that it had handed over the Dolours Price tapes and transcript were untrue. The tapes were passed into the possession of the Department of Justice after a court ruling last year.
The college said it assumed the department handed the tapes over to the PSNI, but could not be certain. It said reports last weekend that more transcripts or tapes were handed over were not true, and these remain in its possession for the time being.
Jack Dunn, the public affairs director at Boston College, said last week that he did not know if the Price tapes had been handed over to the PSNI by the department, and "it's not my place to speak for them. They could have. The DoJ have been in possession of the Price tapes for more than a year. They've had them since January 2012".
He pointed out that the contents of the Price tapes had already been widely reported in Ireland, where she gave extensive interviews to the media.
Mr Dunn said in an interview: "She referenced the tapes in those interviews and mentioned she drove a getaway car and she implicates Gerry Adams in the tapes too. Those things have been disclosed repeatedly.
"There's nothing on the Dolours Price tapes that will be a surprise. There's no reason for the tapes not to be sent to law enforcement, because the legal recourse of the United States has been exhausted regarding the Dolours Price tapes."
In relation to the remaining 11 tapes from the seven other IRA members, he added: "The college has until the end of the month to decide whether to accept or appeal that court ruling. We're in the process of making the determination as to what we will do over the course of the next several weeks."
Seamus McKendry, the husband of Mrs McConville's eldest daughter, Helen, said yesterday: "We are not certain what use the (Dolours Price) tapes will be. The sad thing is she was available for questioning while she was alive in either jurisdiction but there was no action taken despite her living admissions in the media. They waited too long.
"We are exploring the idea of a civil action. We have spoken to lawyers and are considering this. The Omagh families took their action after there was no justice for them."