Mr Justice Peter Charleton said he would also consider if the premise that Ms O’Sullivan relied inappropriately on unjustified ground to discredit a garda whistleblower was based on leaks and conjecture.
He was speaking as the tribunal completed hearings from witnesses in its third module.
The remit of latest module was to examine whether unjustified grounds were inappropriately relied upon by the former garda commissioner Ms O’Sullivan to discredit whistleblower Sgt Maurice McCabe at the O’Higgins Commission of Investigation.
The commission, which sat in private in 2015, investigated complaints made by Sgt McCabe about certain policing matters and about serious allegations against senior officers including then Garda commissioner Martin Callinan.
Mr Justice Charleton outlined 11 questions he said he will have to consider in preparing his report.
He said the first issue was whether false allegations of sexual abuse had been relied upon by the Garda commissioner. He said that “everyone seems to be agreed that there weren’t”.
He said the question remained whether any other unjustified grounds were inappropriately relied upon by the commissioner.
In considering this, the chairman said, he would have to consider were the limits appropriate in cross-examining witnesses, and whether there was evidence the commissioner intended to challenge the credibility of witnesses in an ordinary way.
Mr Justice Charleton also said he would have to consider whether a letter setting out the garda commissioner’s legal position in May 2018 was “a mistake, an uncorrected mistake that was allowed to stay in an inaccurate form due to recklessness or perhaps inadvertence, or was it deliberate?”
In addition, whether the barrister for the gardaí made a mistake “in the heat of the moment” at the commission in saying Sgt McCabe’s integrity was to be challenged.
The chairman said he would also have to consider if there was any evidence of a “dark truth” that the garda commissioner or any other senior officers were “going after” Sgt McCabe at the O’Higgins Commission.
The chairman would also have to consider if the former minister for justice Frances Fitzgerald and her department behaved lawfully in leaving any question of legal strategy to the garda commissioner.
The chairman said it seemed to him that the O’Higgins Commission had handled all matters before it appropriately.
He said he would have to consider whether there was basis for the module or had it been based entirely on leaks and conjecture.
The tribunal will hear submissions from legal representatives next Tuesday in relation to the first module held last summer, and plans to begin hearings on its final module shortly afterwards.
Earlier, deputy commissioner John Twomey told the tribunal he was involved in ensuring workplace supports were put in place for Sgt McCabe, but he “wasn’t involved in any discussions with the commissioner about the legal strategy”.”
Ken O’Leary, a former Department of Justice deputy secretary, said the department felt it could not ask the commissioner what her legal advice was relating to the commission because it would set a precedent.
“We felt that we couldn’t ask the commissioner what advice she had,” Mr O’Leary said, adding that there were limits to what the department could ask about the O’Higgins Commission, whose hearings were held in private.
Noel Waters, the former secretary general in the Department of Justice, said he had not remembered a meeting in May 2016 with the minister, but his memory was refreshed when he was shown notes of the meeting taken by the minister’s advisor.
He said there was an agreement among those present at the meeting that publishing the garda commissioner’s legal advice would be a “a bad idea” and would be “setting up a very dangerous precedent”.