Mr O'Brien's former accountant, Mr Phelan, told the tribunal he gave no instructions to sell or move shares owned by Mr David Austin, the Fine Gael fundraiser, after he died in November 1998.
In September of that year, Mr Phelan said, under instruction from Mr O'Brien he had transferred money to an account of Mr Austin's with Donaldson, Lufkin & Jenrette (DLJ) in New York.
The amount of $295,250.40 was for the purchase of 12,000 Esat Telecom shares.
Mr John Coughlan SC, for the tribunal, questioned Mr Phelan about the transaction.
Mr Phelan said the money to purchase the shares came from Credit Suisse First Boston. He had carried out the transfer of the money on the instructions of Mr O'Brien.
Before that transaction there were 6,600 shares in Mr Austin's name in the account.
Mr Coughlan said a statement from DLJ showed a total of 18,600 shares were still in the account on October 30th, 1998, two days before Mr Austin died.
Mr Coughlan asked what happened to the shares after Mr Austin's death.
Mr Phelan said he believed they were transferred to the account of Mr Noel Walsh.
"It appears there was an error in how these shares ended up in Mr Austin's account," he said.
Mr Phelan said he had been in contact with DLJ representatives, who would come back to him with a full reply in relation to the matter.
Mr Coughlan asked Mr Phelan if the mistake was made by him.
"No, I did not make the mistake in relation to where I was transferring the money," he replied.
Mr Coughlan asked if Mr O'Brien would have known the money was going into Mr Austin's account.
"I would take it he did. It's a fair sum of money," he said.
Mr Coughlan asked Mr Phelan to confirm that he had not given any instruction to DLJ to sell or move shares out of Mr Austin's account.
Mr Phelan said he had not.
He was also questioned about the transfer of $50,000 to Mr Austin's account in February 1998. Mr Phelan was asked if he had carried out the transaction. He said he had not, and that Mr O'Brien must have dealt with the matter himself over the telephone.