Gerry Adams has always denied any involvement in the killing of Jean McConville but audio tapes of a former IRA Commander recovered from an American university has cast doubt on his claim.
Former members of the organisation gave up the secrets of the past to researchers. The interviews were not to be released until after the death of those involved, but police have accessed the tapes.
Mr Adams' old friend, a former IRA Commander, Brendan Hughes, said: "This woman was taken away and executed. Jean McConville.
"There's only one man that gave the order for that woman to be executed. That man is now the head of Sinn Fein. I did not give the order to execute that woman. He did."
Adams attacks reasons for his detention and denies McConville murder
It is claimed IRA volunteers described what happened the night Jean McConville was murdered to Boston College's "Belfast Project".