Former Garda commissioner Nóirín O’Sullivan has said she fully supported Garda whistleblower Maurice McCabe both before and after the O’Higgins commission.

Ms O’Sullivan has concluded her third day of evidence in Dublin Castle at the Charleton tribunal, also known as the Disclosures tribunal, which is investigating if she tried to use “unjustified grounds” to try to discredit Sgt McCabe at the O’Higgins Commission hearings.

The commission sat in private to investigate allegations made by Sgt McCabe of Garda corruption and malpractice .

Ms O’Sullivan is expected to be recalled to the tribunal as a witness on a later date to deal with other matters being examined by the tribunal.

On Wednesday afternoon she insisted she never instructed Garda lawyers to question Sgt McCabe’s integrity during the commission. She said she did not known why her lawyers said those were their instructions.

She was questioned by her own counsel, Shane Murphy SC. She told counsel she full supported Sgt McCabe and that she put in place several measures to ensure his welfare while she was commissioner.

She said she took the Sgt McCabe’s allegations of corruption “extremely seriously”.

Ms O’Sullivan said she took the allegations seriously both because of the impact they were having on public confidence in the force and because she had a duty to vindicate the rights of the gardaí involved.

She added these gardaí had “vehemently” denied the allegations.

This included allegations of corruption against her predecessor as commissioner Martin Callinan, who had been accused of improperly promoting a superintendent in the Cavan/Monaghan area.

She agreed with counsel that the O’Higgins commission stated there was “not a scintilla of evidence” to support this accusation.

Mr Murphy also took her through several other allegations made by Sgt McCabe which were withdrawn or found to be unfounded by the commission.

Earlier, Ms O’Sullivan repeated she “was at a loss” to understand why Sgt McCabe felt under threat from her shortly after her lawyers said they had been instructed to question his integrity at the O’Higgins Commission.

At the tribunal on Wednesday morning, counsel for Sgt McCabe Michael McDowell was asking the former commissioner about a conversation between Sgt McCabe and his district superior in which the whistleblower said he was stepping down as sergeant in charge of the traffic division because he felt under threat from Ms O’Sullivan.

This conversation happened shortly after lawyers for Ms O’Sullivan and other senior gardaí had told the commission they intended to question the whistleblower’s integrity in making corruption allegations against gardaí. Ms O’Sullivan denies instructing her lawyers to take this strategy.

Mr McDowell asked how it was possible she and other senior gardaí and Department of Justice officials did not question if Sgt McCabe’s feeling of being under threat might be connected to his appearance as a witness at the O’Higgins commission.

“I knew he was a witnesses at the commission but I was at a loss to understand why he felt under threat from me,” Ms O’Sullivan replied.

Mr McDowell suggested perhaps she was being “starved of information” of what was happening at the commission. Ms O’Sullivan replied her liaison, Chief Superintendent Fergus Healy, was keeping her up to date.

He said she thought maybe something happened to Sgt McCabe in the course of his work in Mullingar to make him feel under threat.

“Are you serious about that?” Mr McDowell replied. He questioned how could this be so if Sgt McCabe was giving evidence at the O’Higgins commission in Dublin at the time.

Ms O’Sullivan repeated that she did not know why he felt under threat.

Mr McDowell has now finished questioning Ms O’Sullivan. She is now being questioned by Patrick McCann SC who is acting for the Department of Justice.

At the end of his questioning this morning, Mr McDowell asked Ms O’Sullivan about a note from a meeting she had with her lawyers immediately before her appearance at the O’Higgins commission in November 2015.

The note, which was made by her liaison at the commission, Chief Superintendent Fergus Healy, states the commissioner was asked if she would “consider withdrawing.”

Mr McDowell suggested this was a reference to withdrawing the legal strategy of questioning the integrity of garda whistleblower Sgt McCabe when he made allegations of garda corruption at the commission.

Ms O’Sullivan has previously denied giving any such instructions. She said she instructed lawyers to question Sgt McCabe’s motivation and not his integrity.

Counsel asked her how she accounted for this note which was made immediately before her lawyers informed the commission that they had been mistaken when they indicated they were questioning Sgt McCabe’s integrity, five months earlier.

The former commissioner said she could not have instructed that her lawyers withdraw from that strategy since she had never instructed them to follow it in the first place.

She said she could not account for the note mentioning withdrawal, as it was Chief Supt Healy’s note. “I have no recollection of discussing withdrawal,” she said.

Mr McDowell put it to her that this was “simply unsatisfactory.”

Earlier, Ms O’Sullivan denied there was a conflict of interest in having the same legal team represent both her and other gardaí accused of corruption in 2015.

Mr McDowell put it to Ms O’Sullivan that it was improper that lawyers representing gardaí who had an “extremely hostile” attitude to Sgt McCabe also represented her interests at the O’Higgins commission.

Mr McDowell put it to Ms O’Sullivan that sharing a legal team was a “manifest conflict of interest”. She replied that if there was a conflict her lawyers would have told her so.

She previously told the tribunal it was standard policy to have a single legal team representing senior gardaí.

Mr McDowell pointed out she shared a senior counsel, Colm Smyth, with Superintendent Noel Cunningham, a man who was “vehemently of the view that McCabe was trying to destroy his career”.