A US court decision almost two years ago was the catalyst behind the arrest and questioning of Gerry Adams over the murder of Jean McConville.
In 2001 Boston College, Massachusetts, commenced a five-year oral history project aimed at documenting perspectives on the Troubles from those involved in the conflict.
Former paramilitaries, both republican and loyalist, were interviewed about their roles in the 40 years of violence that blighted Northern Ireland.
Journalist and published author Ed Moloney worked on the archive with former IRA member turned writer and academic Anthony McIntyre. They were effectively sub-contracted by the college to undertake an initiative it agreed to fund and store.
The participants - "terrorists" to some, "former combatants" to others - took part on the undertaking that their accounts would only be made public upon their death.
When one such interviewee, former IRA commander in Belfast Brendan Hughes, died in 2008 it emerged that on the tapes he alleged Mr Adams was a senior IRA leader during the Troubles and had ordered Mrs McConville's killing - claims the Sinn Fein leader vehemently contested.
Prior to her death in 2013, Old Bailey bomber Dolours Price made it public that she had also given an interview to Boston College about Mrs McConville's death in which she made similar allegations about Mr Adams. Again, the Louth TD rejected the claims.
The revelations prompted lawyers representing the PSNI to launch a legal bid in the US to obtain the Boston College tapes that touched on Mrs McConville's death.
A long court battle ensued but in 2013 the PSNI won and the college was ordered to pass over the tapes.
Having taken time to examine their contents, detectives ramped up their investigation in the early months of 2014, making a series of arrests, including Mr Adams.
The Sinn Fein supremo claimed most of the evidence detectives presented to him in Antrim police station was based on allegations levelled on the tapes by Hughes and Price.
The PSNI, having only gained access to the tapes about Mrs McConville's death, later moved to seize others. It now has in its possession tapes recorded by both loyalists and republicans, touching on a range of Troubles murders.
Some of the interviewees have threatened to sue Boston College over its handling of the issue.
Both Moloney and McIntyre have also criticised the college, claiming it did not robustly challenge the initial PSNI court bid.
The college has rejected the criticism and has insisted it handled the archive project appropriately.
Read more here: