The Special Criminal Court heard today two mobile phones allegedly lent by Mr Colm Murphy to those responsible for the Omagh bombing were used in the town an hour before the atrocity.
The court was told there were "overt acts" proving Mr Murphy, from Co Louth, conspired to cause the explosion. He denies the charge.
Mr Tom O'Connor SC, prosecuting, said Mr Murphy's phone was used in Omagh at 1.57 p.m. on February 15th, 1998.
A second mobile, allegedly borrowed by Mr Murphy from an unwitting employee, was used in the town at 2.09 p.m.
Fifty-six minutes after the second telephone call the bomb exploded in Market Street, killing 29 people - including a woman seven months pregnant with twins. More than 200 others were injured in the attack.
Mr O'Connor said the prosecution had demonstrated Mr Murphy participated in a conspiracy to cause an explosion in Northern Ireland on the weekend of the atrocity.
"The form that conspiracy took was to loan two mobile phones to persons he knew, or contemplated, wanted those phones to carry out a bombing run to Northern Ireland".
He added: "There was no evidence that Mr Murphy knew exactly where the explosion was to take place. But the explosion to which he lent his aid was in fact that explosion in Omagh".
Mr O'Connor accepted the prosecution case hinged on confessions Mr Murphy allegedly made to officers after his arrest. Mr Murphy claims that these admissions were fabricated.
Mr O'Connor also told the court Mr Murphy's mobile phone was active in Banbridge, Co Down, two weeks earlier where there was an explosion that injured 38 people.
Today is the 22nd day of the trial of Mr Murphy (49), a building contractor and publican who is a native of Co Armagh with an address at Jordan's Corner, Ravensdale, Co Louth.
He has pleaded not guilty to conspiring in Dundalk with another person not before the court to cause an explosion in the State or elsewhere between August 13th and 16th, 1998.
PA