Mahmoud Fustok, a Lebanese-born Saudi Arabian diplomat and brother-in-law of the Saudi crown prince, was an extremely wealthy businessman and horse breeder who for many years was friendly with the former minister for health, Dr John O'Connell.
In 1985, Mr Fustok gave £50,000 to the late Charles Haughey, the money being conveyed to the then leader of the opposition by way of Dr O'Connell.
The tribunal is expected to reject evidence from Mr Haughey that the payment was for a yearling he sold. He corresponded with the tribunal, but never attended to give evidence. Mr Fustok died earlier this year when he was knocked down by a sports utility vehicle while out jogging in Pompano Beach, Florida.