At the very early stages, the inquiry was told by senior counsel for Ms O’Sullivan that evidence would be produced to show that Sgt McCabe had told two other officers that he was making his complaints because of malice he harboured towards a senior officer.

The inquiry was informed that the two officers had taken notes at the meeting in question and prepared a report which was forwarded to a senior officer.

However, a few days after the submission, Sgt McCabe informed Mr O’Higgins he had a tape recording of the meeting in question.

The commission took possession of the recording and arranged for a transcript to be created.

Mr O’Higgins indicated that the transcript coincided precisely with Sgt McCabe’s version of events and was in conflict with the allegation that he had told the two officers he was motivated by malice.

Maurice McCabe

Following that, no evidence to show malice was called from the two officers who were at the meeting.

However, the failed attempt to impugn Sgt McCabe’s character did not appear in the O’Higgins report. The retired judge stated that Sgt McCabe was an entirely truthful witness and his bona fides were fully accepted.

The documents show that, at the commission, Mr O’Higgins asked the commissioner’s lawyer whether “you are attacking his [McCabe’s] motivation and attacking his character”.

The reply from Colm Smyth, SC, was: “Right the way through.”

He told the judge that he was acting on instructions.

Sgt McCabe’s counsel, Michael McDowell, objected in the strongest terms to the course being taken by Ms O’Sullivan.

“Attacking one of our own members of our force who is in uniform and on oath when in circumstances where in public she promoted him to a professional standards unit, and in public she has indicated that she accepts that he was acting in good faith et cetera, et cetera, and in private she sends in a legal team to excoriate him.”

Nóirín O’Sullivan

At the inquiry, the commissioner was represented by the same counsel as two of the officers against whom Sgt McCabe had made allegations.

A Garda spokesperson said the commissioner was barred by statute from commenting on the commission.

In May 2014, then acting commissioner Ms O’Sullivan told a joint Oireachtas committee that Sgt McCabe had the full support of garda management.

In September 2014, after Sgt McCabe raised further concerns about the penalty points system, the commissioner appointed him to the Professional Standards Unit to assist in reforming the system.

The O’Higgins report published on Wednesday described Mr McCabe as a dedicated and committed officer. It said the sergeant was “a person who acted out of genuine and legitimate concern” and that the commission “unreservedly accepts his bona fides”.

The inquiry vindicated former justice minister Alan Shatter, who had resigned after criticism of him in the Guerin Report, which preceded O’Higgins.