Irish Mail on Sunday journalist Debbie McCann has told the Disclosures Tribunal that she was not negatively briefed by any garda member on Sergeant Maurice McCabe.
Ms McCann also said she has no evidence of any orchestrated campaign against him by garda management.
The journalist was named by former garda press officer Superintendent David Taylor as one of 11 journalists he alleges he negatively briefed about whistleblower Sgt McCabe.
Ms McCann said that in February 2014, she heard murmurings about Sgt McCabe and some allegation in his past.
Asked if she contacted Supt Taylor to find out and whether the murmurings were from him, Ms McCann said she could not answer for source reasons.
Mr Justice Peter Charleton said he did not know where source protection could come up in that instance and he asked whether Ms McCann did ring Supt Taylor.
She said she could not answer but no garda member ever briefed her negatively about Sgt McCabe.
Ms McCann said she found out from her enquiries that the allegation against the sergeant related to inappropriate touching and that the Director of Public Prosecutions ruled that there should be no prosecution.
She said she found out names and that the complainant was the daughter of a garda colleague.
Patrick Marrinan, for the Tribunal, put it to Ms McCann that Supt Taylor has told the tribunal that Ms McCann phoned him before she went to Cavan to try to interview the complainant, Ms D.
Ms McCann said she could not confirm that as she had to protect her career as a journalist and she was not comfortable revealing whether she discussed the matter with Supt Taylor.
Mr Justice Charleton said to Ms McCann that she had a fundamental patriotic obligation to tell the truth and that she had sworn an oath. Ms McCann said she took that very seriously.
Ms McCann also denied that she had issued a blanket refusal to co-operate with the tribunal in her initial responses to the inquiry, through the Mail's solicitor.
Mr Marrinan also put it to Ms McCann that she had refused to supply her mobile number and and refused to answer any of the tribunal's initial questions.
Ms McCann said she had subsequently provided more detail and answered questions about text messages.
She said she did not supply her mobile number because she did not want to give rise to investigations into her number that might identify her sources.
Mr Marrinan said the tribunal was not looking into her sources.
Ms McCann also denied that she was told by former garda commissioner Nóirín O'Sullivan about a child sexual assault complaint against Sgt McCabe.
Another Irish Mail journalist, Alison O'Reilly, has told the tribunal that Ms McCann told her, her information was coming from the top of the gardaí, from Ms O'Sullivan.
Ms McCann said today that conversation did not happen and she said there was no communication between her and the former commissioner during that period.
Ms O'Sullivan has also told the inquiry she never spoke to Ms McCann about Sgt McCabe.
Ms O'Reilly also gave evidence that Ms McCann told her that Sgt McCabe was a child abuser and that she got the name and address of the complainant, Ms D, from someone high up in An Garda Síochána.
Ms McCann denied both those statements. She also rejected an assertion that her father, a retired superintendent, had confirmed the Ms D story to her.
Mr Marrinan, for the tribunal, asked Ms McCann if Supt Taylor gave her the information on Ms D. Ms McCann said that nobody guided her in her job.
Ms McCann declined to answer a series of questions in response to Supt Taylor's evidence on their discussions due to "source protection".
Sgt McCabe's lawyer, Michael McDowell, said he would be making a submission that Ms McCann's failure to give straight answers strongly implied that Supt Taylor did impart information to her about allegations against Sgt McCabe.
Ms McCann said she did not wish that inference to be taken from what she was saying.
Supt Taylor's lawyer, Michael O'Higgins, put it to Ms McCann that based on the phone records, she was in contact with their former Garda press officer so often that it was inconceivable that they did not talk about Sgt McCabe.
Ms McCann said she was not going to answer that question and she was not going to talk about conversations off the record.
He also said that Supt Taylor says he did not direct Ms McCann to go to Ms D's house.
Earlier the Security and Crime Editor of The Irish Times, Conor Lally, described as "total fantasy" a claim by Supt Taylor that the journalist pushed back when he tried to brief him negatively about Sgt McCabe.
Mr Lally was giving evidence for a second day to the Disclosures Tribunal, which is examining an allegation of a smear campaign against Sgt McCabe.
Supt Taylor previously told the tribunal that Mr Lally was the only one of the journalists he claims to have negatively briefed about the whistleblower, that ever pushed back on anything he was saying.
He said that when he told Mr Lally that Sgt McCabe had not co-operated with an internal garda investigation into penalty points, Mr Lally had said he did not believe it.
Mr Lally told the tribunal that if that conversation had happened as the superintendent outlined then he would recall it, but he said it never happened.
He said he was never briefed by any member of An Garda Síochána against Sgt McCabe.
He said Supt Taylor had no evidence to back up his claim and could not say where or how many times he had spoken to him.
The tribunal also heard that Mr Lally had a conversation with an individual, which he believes may have been in 2010 or 2011, during which the individual told him about a 2006 allegation against the sergeant which was dismissed by the DPP, and said that Sgt McCabe had fallen out or had an issue with Garda management.
John Ferry, Counsel for Supt Taylor, put it to Mr Lally that the information Supt Taylor claims to have given him about an agenda from Sgt McCabe might not have startled him if he had already heard it referenced during the conversation in 2010 or 2011.
Mr Lally said the person he had spoken to previously was not a garda and did not have a garda agenda.
He said the person was answering questions Mr Lally had asked, and the conversation was not part of any campaign to do down Sgt McCabe.
Mr Ferry put it to Mr Lally that perhaps he just did not remember being negatively briefed against Sgt McCabe by Supt Taylor.
Mr Lally said if anybody from An Garda Síochána had come to him to try to smear the sergeant, he would recall it as it would have been a big moment.
Additional reporting Sinead Morris