Tribunal witnesses are fast coming to resemble fairground dodgems, their rival versions of the truth bumping into each other with alarming regularity.
Mr Gay Grehan, the former director of the Murphy group who tipped off Mary Harney about the Burke payment, is familiar with this experience; on his last visit to the witness-box in May, his evidence ran counter to that given by the Tanaiste, two tribunal lawyers and, ultimately, himself.
That saga led to one of the big blow-ups of this tribunal, with Mr Garret Cooney SC, for the Murphy group, accusing the tribunal lawyers of "dubious ethical standards" after Mr Grehan disputed the statement drawn up for him by the tribunal.
Yesterday, Mr Grehan was knocking into rival versions again, but this time it was the Murphy group that felt the jolt.
Mr Grehan's testimony suggests the company knew far more about the payment made from its accounts to Mr Ray Burke than it was prepared to admit in 1997.
In June of that year, Mr Joseph Murphy jnr told Mr Dermot Ahern of Fianna Fail that Murphys made no payment to Mr Burke. The Taoiseach had given Mr Ahern the job of interviewing Mr Murphy about the rumours then circulating about Mr Burke.
However, Mr Grehan said yesterday two company executives told him in late 1996 that £30,000 had been paid from the accounts of Joseph Murphy Structural Engineering. At least one of them told him the money went to Mr Burke.
He said he talked to the accountant, Mr John Maher, and the managing director, Mr Frank Reynolds, and they assured him the money had been paid back to JMSE from another Murphy account within two weeks. That was the extent of his inquiries and both men told him they were satisfied with the matter, he said.
He claimed he and the other two executives first learned of the payment of £30,000 to Mr Burke when the journalist Frank Connolly came to them with the allegations.
The only trouble with this version is that Mr Connolly came to JMSE with an allegation that £40,000, and not £30,000, had been paid, having been told this by Mr James Gogarty. So how could the company trace such a payment when it was told the wrong amount? And having done that, how could it then say it was unable to track the money paid to Mr Burke until after the tribunal started?
Mr Grehan, who left JMSE in 1997, again proved a nervous witness and had to be reminded constantly to speak up.
His wife, former Progressive Democrat candidate Dr Mary Grehan, spent the afternoon vigorously nodding or shaking her head as the various questions were put to her husband.
Mr Justice Flood had earlier decided not to delve into the area of dispute between the Grehans and the tribunal lawyers by ruling out the draft statement prepared by Mr Pat Hanratty SC and Mr Des O'Neill SC after they interviewed Mr Grehan last December.
Mr Grehan seems to have told the lawyers during this interview that he knew about the Burke payment back in 1989/90, but in subsequent evidence he said this was "inadvertently incorrect". In other words, he said it by mistake.
Mr Denis McCullagh SC, for the Grehans, convinced the chairman that the tribunal had nothing to gain by re-entering this "trial within a trial". Either Mr Justice Flood could come down on the side of his legal team, leaving himself open to a perception of bias, or he could support the Grehans, which might leave his lawyers in a difficult situation.
For that reason, and because Mr Grehan had no direct involvement or firsthand knowledge of the bribery allegations, Mr McCullagh argued that the chairman should drop the matter, and excise the evidence Mr Grehan and the tribunal lawyers have already gi ven. The Murphy legal team supported him.
Mr Justice Flood agreed with Mr McCullagh that the main difference between the conflicting statements related to the date at which Mr Grehan learned of the allegations of the Burke payment.
But the differences turn on a lot more than a disputed date. In the draft affidavit prepared by the tribunal lawyers and later disowned by Mr Grehan, senior managers in JMSE are fully aware of the payment; in his own statement, Mr Grehan put his knowledge down to "rumour and hearsay".
The disputed statement emphasises that the money was paid for planning favours and that Mr Gogarty was not centrally involved; the second statement does not.
Because no evidence will be taken on the disputed statements, there would seem to be no need to hear evidence from Dr Mary Grehan, who was present when the interview with her husband took place. However, Dr Grehan intervened yesterday to say it was her wish to give evidence.