The three journalists, security correspondent Cormac O’Keeffe, political correspondent Juno McEnroe, and political editor Daniel McConnell, said the principle of journalistic privilege precluded them from providing testimony that might in any way identify sources.
Their stance came under rigorous questioning from the tribunal chairman, Judge Peter Charleton, who disputes its validity.
Supt Taylor, the former Garda press officer, has told the tribunal that the three were among 11 journalists he briefed negatively about Sgt McCabe. He has waived privilege and asked them to corroborate his testimony.
They argued that wider issues were at stake and for a journalist to abandon the principle of privilege would have a “chilling effect” on dealings with sources in future — a point recognised by the European Court of Human Rights.
Mr O’Keeffe confirmed he had heard some rumours about Sgt McCabe in early 2014. He was taken to task by Judge Charleton for declining to answer questions about the categories of people who might have spread these rumours.
“My fear is that, by answering the general question, I will directly, if not indirectly, answer the specific questions. I can not do that,” he said.
“My overriding obligation is not to do anything that would endanger the flow of information from sources to journalists, either now or in the future.”
Mr McConnell said he had also heard “chatter” about Sgt McCabe but that he shared Mr O’Keeffe’s stance.
He said that, if he did otherwise, “the conclusion would be that Daniel McConnell is a person who, when pressure is brought to bear, will sing like a canary”.
Mr McEnroe said he had heard “gossip and prattle” about Sgt McCabe in 2014 but it was much later when he discovered that it related to allegations of sexual assault.
Judge Charleton expressed frustration that this was not made clear earlier. He said Mr McEnroe initially told the tribunal by letter he had no information relevant to it when he was now claiming privilege and neither confirming nor denying that he had such information.
Mr McEnroe acknowledged his original response was incorrect. The tribunal had sent correspondence to the wrong address and left him up against deadline in furnishing his response, which he said was “rushed”.
Judge Charleton accused him of not being helpful and of not trying to answer questions.
“You are playing games,” he said.
Mr McEnroe replied: “I reject that.”