Probably not, but what if that conversation was about something really important? Would you not remember the content of that exchange a lot longer, or at least recall that there was a conversation?

A feature of the recent hearings of the Disclosures — known as Charleton — Tribunal was the failure of a number of people to remember conversations or communications that occurred at a time of great upheaval, or, at the very least, excitement.

Central to the issue being examined by the tribunal were events over the weekend beginning Friday 15 May 2015. That was the second day of hearings into the O’Higgins commission, examining Sergeant Maurice McCabe’s complaints of malpractice.

The hearings were in private. On the Friday afternoon, Judge O’Higgins was told by counsel for then commissioner Nóirín O’Sullivan and other senior gardaí, Colm Smyth, that he would be challenging Sgt McCabe’s motivation in making the claims. This sparked a major row both inside and outside the hearings.

Going after Sgt McCabe in this manner would be in complete contrast to the attitude the commissioner had displayed towards him in public. She had lauded his actions in bringing forward the complaints. She had praised his assistance in sorting out the ticket-fixing scandal.

Now she was going to question whether he may have been motivated by a grudge. This, she told Charleton last month, left her with an “almost impossible dilemma”.

Everybody knew what was unfolding was big potatoes. The state solicitor representing Mrs O’Sullivan and others, Annmarie Ryan, noted that it was “political dynamite”.

During that afternoon and over the following days there was a flurry of activity in response to the unfolding situation. What emerged last month is that despite the stakes, the protagonists, the implications, a lot of people remember very little about much of it.

An email outlining the row and fall-out was sent to a number of people in the Department of Justice. Acting secretary general at the department Noel Waters has no recollection of it.

“I’ve no recollection of reading the email,” he told the tribunal.

That afternoon he had a 14-minute conversation with Nóirín O’Sullivan. He doesn’t remember what that was about.

“And I think she says she has no recollection of the conversation either,” Mr Waters told the tribunal.

That was kind of correct. When Ms O’Sullivan was talking to the tribunal’s investigators last November, she couldn’t remember it. By the time she came to give evidence in January, she remembered it “In the context of the security operation” that was being mounted for a royal visit at the time.

Still no recollection of a conversation about an issue which was presenting for her an “almost impossible dilemma”.

The department was contacted about the row through the attorney general’s office, but few if anybody in the department can remember anything about the email, or other emails generated, or any conversations about it.

One official, Martin Power, was asked whether he discussed the email with the then justice minister Frances Fitzgerald.

“I don’t recall that I personally had any discussions with the minister at this time,” he told the tribunal.

Tribunal lawyer Patrick Marrinan put this point to assistant secretary at the department Ken O’Leary, who had been central to much of the communications.

“So on the one hand everything seems to be well-documented, people have a recall of what took place, it seems to have been done officially, but on the other hand we have a lack of recall, no notes, no documentation, no emails and no reference to this having occurred in any of the emails?” the lawyer asked.

Mr O’Leary replied: “I see exactly the point you’re making.” He suggested the problem was time pressures.

Afterwards, it was discovered that despite the political dynamite, an apparent major “error” had been made in the preparation of a vital document that weekend.

The error cast Sgt McCabe as a man attempting to blackmail a senior officer. It was discovered after Sgt McCabe produced a recording from a disputed meeting and a contemporaneous report from the meeting corroborated his version.

This was more big potatoes. But did anybody tell the commissioner, and what had she to say about this situation in which she had been placed?

Her liaison officer at O’Higgins, Chief Superintendent Fergus Healy, told the Charleton Tribunal he told her, but when, and where and what was her reaction to this devastating news?

“I can’t remember specifically,” the chief super told the tribunal.

In any event, his boss couldn’t remember a few other significant conversations. She met her senior counsel for the first time on May 21, the week after the row, but she can’t recall if they spoke about what must have been a major issue at O’Higgins. “I just have no recall of the meeting,” she said of it.

She was also asked about another element of the McCabe case which should have made her hair stand on end. The previous year, she had received a letter which erroneously stated that there had been an allegation of child rape against Sgt McCabe.

These were scurrilous lies, the apparent result of a clerical error, but Ms O’Sullivan didn’t know that. What did she think when she read the communication?

“I have no recollection of that letter specifically being brought to my attention,” she told the tribunal.

One other issue that is stretching the memory bank was the reaction to Sgt McCabe when the erroneous document was produced. He immediately stepped aside from his position in charge of the traffic unit in Mullingar, citing that he felt “under threat” and referencing the commissioner. He believed senior management were out to fit him up.

At the tribunal, the official in charge of policing in the department, Michael Flahive, was asked whether he had been made aware of this serious, and potentially damaging development.

“I don’t recall being aware of it,” he replied.

There is no doubt that memory can play tricks. The human memory bank is not a computer, and allowance must also be made for unconsciously filtering out communications that are not important.

Yet it is somewhat surprising that memory did fail so many about an issue of such political dynamite at the time.

Acting secretary general of the Department of Justice, Noel Waters, on receiving the email about the row at the O’Higgins Commission on 15 May 2015.

- Q: Surely, at that stage, reading it, you said, what in heaven’s name is going on here? We made a decision that was not to be considered by the O’Higgins Commission, and here counsel is raising it?

- A: All I can say in response is what I’ve said earlier, I’ve had — I’ve no recollection of having read the email.

Mr Waters questioned about 14-minute phone call with Nóirín O’Sullivan that day.

- Q: And you’ve no recollection of a conversation on which, on the face of it, Nóirín O’Sullivan, at the very central point in time when she was dealing with this issue, is supposed to have had with you on the previous Friday?

- A: That’s correct, yes. And I think she also says that she had no recollection of the conversation either.

Chief Superintendent Fergus Healy on telling Nóirín O’Sullivan about the “error” in the letter designed to challenge Sergeant McCabe’s motivation.

- Q: Was Commissioner O’Sullivan informed at some stage of what had transpired on day five, can you remember? She had to have been told sometime but I was just wondering when you told her?

- A: I can’t remember specifically.

- Q: Yes. So do I take it from that, chief superintendent, that there was no sense of a catastrophe or a big mistake having been made or something having gone very badly wrong?

- A: Well, obviously the implications of the paragraph itself had a completely different meaning and at some stage, I would have spoken to her about it and told her about it.

- Q: Yes.

- A: But I would have explained that this was a genuine error that had occurred and it had been explained to the commission what had happened. And I think the –

- Chairman: You have no specific recollection of that conversation at all?

- A: I don’t, I don’t, sorry.

Nóirín O’Sullivan questioned about the referral of a completely false allegation of sexual abuse against Sergeant McCabe in July 2014.

- Q: And your then-private-secretary, when he gave evidence to the tribunal in July, seemed to be under the impression that you read that referral at that time and the letter that was sent to your office by Assistant Commissioner Kenny in relation to the matter?

- A: I have heard — or read Superintendent Walsh’s evidence, chairman. I have no recollection of that letter specifically being brought to my attention, but I don’t dispute what Superintendent Walsh was saying, that he brought it to my attention. I don’t specifically remember it.

On questioning about her first meeting with her senior counsel, a week after the O’Higgins Commission had started and whether they discussed the “error” which cast McCabe in a poor light.

- Q: And you didn’t discuss it, you say, at a meeting three days after this with Mr Smyth, that he had made this error?

- A: Chairman, to the best — I can only say to the best of my recollection, no. But as I say I just have no recall of the meeting.

On that 14-minute phone call with Noel Waters and whether they discussed the “political dynamite” from the O’Higgins commission that day.

- A: I don’t have any specific recollection of speaking to him in relation to this matter, but the fact that I was just off the phone from Chief Superintendent Healy, it is quite likely that I said a legal argument had arisen at the Commission.

Frances Fitzgerald on what she remembered or didn’t remember about the email and the fall-out from O’Higgins on 15 May.

- Q: Yes. We don’t have a record of any other — we don’t have a copy of your note — or, sorry, the printout, with your initials having noted it. But in any event, I think you said yesterday that you read it and you gave some consideration to it?

- A: Well, you know, I haven’t changed in relation to this. When it was brought to my attention some time ago, I didn’t recall the particular email, but when I read the email, I can quite clearly put a broader context on how I would have approached it, or indeed the other email in July, and it would have been the same context that I’d put on it that I would bring to discussions in the Dáil on this or parliamentary questions I was being asked.

So that would have — you know, what I was explaining yesterday is that that would have informed my response to this email or any other email. And, you know, it’s different being asked in general, do you remember an email?

But when you actually look at it, then I can give what my, you know, my best thinking would have been as to how I would have approached it when I read it. So that is what I was trying to explain yesterday.

Q. And you are fairly certain that you didn’t discuss it with anybody else in the Department?

A. I am, yes.