Irish Examiner Security Correspondent Cormac O'Keeffe told the Disclosures Tribunal that he is claiming journalistic privilege and he cannot answer whether he was negatively briefed by Supt Taylor or any other senior garda about Sgt Maurice McCabe.
Mr O'Keeffe has been named by Supt Taylor as one of 11journalists he says he briefed negatively about the sergeant.
Mr O'Keeffe declined to answer any questions on discussions with sources including whether he had heard rumours about Sgt McCabe's character.
He also declined to say whether he had information that would impact on the working of the inquiry.
Counsel for the tribunal, Patrick Marrinan, suggested to Mr O'Keeffe that he was approaching journalistic privilege as an absolute rule and he said the inquiry was not interested in sources other than Supt Taylor.
Mr O'Keeffe said he did not see it that way. He said that journalists had an obligation to protect sources and that was fundamental to press freedom and the free-flow of information.
Counsel for Martin Callinan and Nóirín O'Sullivan, said they would submit that it was unfair to their clients that Mr O'Keeffe has refused to answer a question on whether the former commissioners had negatively briefed him.
Mr Justice Peter Charleton said that based on the state of the evidence on the relationship between Mr O'Keeffe and the former commissioners, it was not conceivable that there was any such communication.
Counsel for Sgt McCabe, Paul McGarry SC, said that in relation to the earlier witness Juno McEnroe, he had provided evidence which was very specific on certain things and then refused to answer other questions, they would submit that the tribunal was entitled to infer that it is possible, on the balance of probabilities, that the witness was briefed or was in the receipt of information.
The Irish Examiner's Political Editor Daniel McConnell told the tribunal this afternoon that he had similar views to his colleague Cormac O'Keeffe in relation to the principle of journalistic privilege.
Mr McConnell told the tribunal he could not confirm or deny whether or not the former Garda Press Officer Supt David Taylor had negatively briefed him against Sgt McCabe.
John Ferry, Counsel for Supt Taylor, said that the superintendent was in a very vulnerable position, that he had put everything that he knew out there and named a number of journalists as people he had negatively briefed, including Mr McConnell.
Mr McConnell said he was not in a position to get into discussing what may or may not have happened, that may or may not reveal a source because of what he saw as the overriding principle of journalistic privilege.
Mr McConnell said he first became aware of the 'Ms D' allegation against Sgt McCabe after the publication of articles by journalist Paul Williams in the Irish Independent in April 2014.
He told the tribunal that prior to that he had heard what he described as "journalistic chatter" in relation to Sgt McCabe in the run up to the Public Accounts Committee meeting in January 2014.
He said the chatter was vague and low level, but was attacking the credibility of Sgt McCabe.
The tribunal chairman, Mr Justice Peter Charleton, said that as Mr McConnell said he had not really heard about the allegation against Sgt McCabe apart from the newspaper article during this time, that it could not possibly be the case that he was negatively briefed by Supt Taylor.
The chairman said that was what was in his head at the moment and that now was Mr McConnell's chance to tell him.
Mr McConnell said he could not confirm or deny the suggestion, and that he was not going to get into a position where something he said might draw the judge to an inference.
Earlier Political Correspondent with the Irish Examiner told the tribunal he could not confirm or deny if he was negatively briefed against Sgt McCabe.
Juno McEnroe is claiming journalistic privilege in relation to his contacts with former Garda Press Officer Superintendant David Taylor.
The tribunal is examining an allegation made by Supt Taylor of a smear campaign against Sgt McCabe.
Supt Taylor has named Mr McEnroe as one of 11 Journalists he claims to have briefed negatively against Sgt McCabe.
The tribunal heard today that Mr McEnroe's solicitors had written to the tribunal in March of 2017 stating that the journalist did not have any information relevant to its terms of reference.
Mr McEnroe also confirmed the contents of the correspondence during an interview with tribunal investigators in April 2018.
Today, Mr McEnroe said he wanted to clarify that the information in the letter of March 2017 was incorrect, and said he regretted the error.
He said he should possibly have had a letter sent which stated that he would be claiming privilege and would not be confirming or denying that he had information relevant to the tribunal.
Mr McEnroe told the tribunal that he did not have any knowledge of any attempt by Martin Callinan, Nóirín O'Sullivan, or other garda of Assistant Commissioner rank upwards to discredit Sgt McCabe by reference to an allegation of criminal misconduct against him.
Asked if he had any evidence of any attempt made by Supt Taylor to discredit Sgt McCabe in this way, Mr McEnroe said he could not answer the question for fear of disclosing information relating to sources.
Mr McEnroe told the tribunal that he was not aware of a 2006 allegation of sexual misconduct against Sgt McCabe, which was dismissed by the DPP, until after July 2014 when Supt Taylor left the Garda Press Office.
Tribunal Chairman Mr Justice Peter Charleton put it to Mr McEnroe that it followed that Supt Taylor could not have negatively briefed him about Sgt McCabe.
The journalist said he had stated that he did not become aware of the allegation against Sgt McCabe until after July 2014, and that he would rather not discuss any conversation he had with a source.
Mr Justice Charleton put it to Mr McEnroe that he had written to the tribunal in 2017 and confirmed in April this year that he had no relevant information.
He said Mr McEnroe had sworn to tell the whole truth, and that meant that when he was asked a question he actually had to give the information.
Mr McEnroe said he was trying to be helpful.
He said he was not denying or confirming that he had been negatively briefed.
Mr McEnroe told the tribunal he did hear what he described as 'prattle' around the time that Sgt McCabe gave evidence to the Public Accounts Committee in early 2014.
He said there was a comment from someone raising a question mark around Sgt McCabe in relation to whether or not he was a trustworthy person.
Mr McEnroe said he spoke to people who knew and had met Sgt McCabe and satisfied himself that the sergeant was credible.
The journalist said he was not sure when he had heard about the allegation against Sgt McCabe, but outlined that it may have been around the time of the O'Higgins Commission, or when the controversy around a Tusla file emerged in early 2017.
Mr McEnroe rejected a suggestion by lawyers for journalist Alison O'Reilly, that he was colluding with gardaí by not revealing his discussions even though Supt Taylor had waived privilege.
Counsel for Mr McEnroe, Oisin Quinn, intervened and said the question was beyond acceptable range.