Former minister for justice and leader of the Progressive Democrats, Mr Des O'Malley, is under pressure.
The man who built his political reputation on toughness and probity - and who refused to accept faulty memory explanations from others - has been asked difficult questions about what exactly happened under his stewardship 31 years ago and what, if any, role he played in the matter.
The original statement of Col Michael Hefferon, former Head of Military Intelligence, was changed to protect Jim Gibbons, a former minister for defence, and to buttress the State case alleging a conspiracy to import arms illegally against two government ministers, Charlie Haughey and Neil Blaney. Also charged were Army officer Capt James Kelly, Belfast republican John Kelly and Belgian businessman Albert Luykx.
In the event, Col Hefferon gave his full evidence in open court. However, that did not alter the fact that his original statement was withheld from the Attorney General, Mr Colm Condon, in preparing the case.
An order of privilege was signed in relation to it by Mr O'Malley during the second Arms Trial at a time when the State legal team was treating Col Hefferon as a hostile witness because counsel believed he had changed his evidence since giving his original statement.
From the beginning, Mr O'Malley has denied that he altered anyone's evidence or that he approved or condoned anyone else doing so. He stated he had no recollection of seeing Col Hefferon's original statement at the time or of signing the claim of privilege.
In the course of a lengthy interview on RTE last night, Mr O'Malley's memory did not improve. He said, however, that the file over which he claimed privilege in 1970 was not the same file which had been released under the 30-year rule earlier this year. Other material had been added to it. The difficulty, he said, was that there was no list of contents and it was "really impossible to tell what was in it in 1970".
That is not the case. Notation on the original Hefferon statement suggests it was one of the first documents placed in the file. The document was marked "seen" by both the Secretary of the Department of Justice, Peter Berry, and Mr O'Malley in May 1970.
Four months later, during the second Arms Trial, privilege was claimed in relation to it.
As for the excision from Col Hefferon's statement of references to Jim Gibbons's knowledge of plans to import arms, Mr O'Malley said these would have been "bits that were inad missable in evidence . . . against any of the accused".
The importance of Col Hefferon's statement ultimately lay not in advancing the State's case but in defending the accused.
Elements of the statement which dealt with the knowledge of Mr Blaney and Mr Haughey in relation to arms importation were not excised.
Mr O'Malley repeated his call for a full inquiry into the Arms Trial and into all matters leading up to it. To concentrate all attention on a single document would be to grossly oversimplify a most complex affair, he declared. He insisted the Government had never authorised the importation of weapons for use in Northern Ireland.
In defending the State and opposing a slide towards civil war in those traumatic days, editing a statement may have seemed a small matter. It was not so. Even at this remove, the matter should be investigated.