The Disclosures Tribunal has heard that a senior garda left the then commissioner in the dark by not relaying that a rape allegation made against Sergeant Maurice McCabe was false.
In 2006, an allegation of child sexual abuse was made against Sgt McCabe which was then dismissed by the Director of Public Prosecution.
In 2013, the allegation resurfaced and was incorrectly inflated to a more serious one.
The Tribunal is examining whether this false allegation was used by senior gardaí to discredit Sgt McCabe.
Retired assistant commissioner Kieran Kenny was asked about his handling of the false allegation from May 2014.
He forwarded the original notification to the commissioner on 16 May 2014 saying that the allegation had previously been investigated. However, he did not send on the corrected notification when he received it.
SC Patrick Marrinan said that until the issue erupted in 2017, the Garda Commissioner only had documents in relation to a rape allegation.
Mr Kenny said he was under the impression that the correction had been sent. He said he could not put it stronger than that. He added that he had a huge amount of responsibilities at the time dealing with policing in 13 counties.
Mr Justice Peter Charleton said the one thing the Garda Commissioner deserved to know was that the allegation was a complete mistake.
Mr Marrinan said that it was not the case that the Garda had made a mistake and were trying to cover their tracks, the error had been made by the HSE.
Mr Kenny also said he regretted that he had not contacted Sgt McCabe at the time given how everything had played out. He said hindsight was a wonderful thing.
He also acknowledged that he had seen the original 2007 investigation file because it had been sent to Seán Guerin as part of the barrister's examination of malpractice issues highlighted by Sgt McCabe.
The tribunal also heard about a meeting to discuss the matter, held in Mullingar on 16 July 2014. Mr Kenny attended, as well as Chief Superintendent Sheridan and Superintendent Leo McGinn. The meeting knew that the mistake had been made.
Mr Marrinan suggested that Mr Kenny was still pushing the false allegation and promoting that it could be re-examined as a criminal offence even though Chief Supt Sheridan had said it was investigated.
Mr Marrinan asked why the matter was not closed off.
Mr Kenny replied that he was teasing out possibilities at the meeting and was also looking at the exposure or risk from an organisational level.
Breffni Gordon BL for Sgt McCabe asked why Mr Kenny had not told the meeting "nothing to see here". Mr Kenny said he was not trying to let the allegation fester.
The tribunal also heard that a meeting was held on 7 August 2014 between the then interim Garda Commissioner Nóirín O'Sullivan, Sgt McCabe, his solicitor and Mr Kenny to discuss workplace issues.
Mr Kenny said he did not inform the commissioner that day that the rape allegation made against the sergeant was incorrect.
In addition, neither the commissioner nor Mr Kenny told Sgt McCabe that the allegation had been made against him. He would not find out until January 2016.
Breffni Gordon BL suggested to Mr Kenny that the meeting was "a golden opportunity" to tell the Garda Commissioner that a grave error had occurred and had remained uncorrected.
Mr Kenny said the meeting only related to workplace issues in Mullingar.
Mr Gordon also said he could have told Sgt McCabe that there was a live, unpleasant file passing between him and the Garda Commissioner on a rape allegation.
Mr Kenny said the onus and responsibility for that was with HSE.
Mr Marrinan said that a reasonable person might say there was a conspiracy to do down Sgt McCabe.
Mr Kenny said he never held any animosity or malice towards Sgt McCabe and he would not engage in such a matter.
The tribunal also heard that in May and June 2014, correspondence was exchanged between Sgt McCabe's solicitors and the Garda Commissioner in relation to workplaces issues he was experiencing.
A dispute arose over whether the Garda Commissioner told Sgt McCabe that she had been given misleading information which she then recounted at the Oireachtas Justice Committee.
This related to Sgt McCabe being provided with workplace supports.
Forensic evidence backs template error in McCabe report
Earlier this morning, the Tribunal heard heard that a forensic examination supports the explanation that a false allegation made against Sgt McCabe was made due to a template error.
The tribunal is examining the Health Service Executive and Tusla's claims that this was a genuine mistake, which was compounded and repeated by a series of errors, and passed on to An Garda Síochána.
The inquiry had previously heard that Laura Brophy of the HSE's Rian Counselling Service made a mistake by incorrectly using a template from another client to fill in a retrospective allegation of abuse made by a Ms D in 2013.
That resulted in a more serious rape allegation being made against Sgt McCabe.
Mark McConnell of Forensic Science Northern Ireland told the tribunal that an examination of the computer used to generated the documents supported this explanation for the error.
He said metadata showed that a Ms Y template had been used to fill in Ms D's form and the documents were not interfered with.