Mobile phone analysis puts Mr Joe O'Reilly's phone near the scene of his wife's murder and is not in keeping with his own account of his movement, an expert witness told the jury at his murder trial today.
Oliver Farrell, of engineering consultancy group Vilicom, explained how mobile phone networks work.
He said the network is built up through a series of telephone masts (base stations), each carrying a number of transmitters which are generally pointed by antennas in three different directions.
He said that the three different directions ensure there is 'surround coverage.'
He said after call or message is made, a signal will be sent out and that the closest transmitter, on the closest mobile phone mast, will pick it up. He said the network will then page other transmitters while looking for the phone.
Because transmitters have a limited amount of capacity, there are more of them covering smaller arcs of coverage in urban areas.
He said smaller areas of coverage are achieved by 'tilting' the transmitters in a downwards direction, as you could a spotlight.
This means there are fewer transmitters in rural than in urban areas and that arcs of coverage are equally bigger.
He said that cell sites must overlap, otherwise there are coverage blackspots. Mr Farrell then traced communications made by Mr O'Reilly's phone the day of the murder
The phone was picked up by masts just North of Swords on the M1, between M50 and M1, and by mast at Finglas garda station between 05:25:05 and 05:45:14. Asked by Mr McGinn whether that analysis corresponds to Mr O'Reilly's own account of going from the house in Belderragh to Jackie Skelly's gym, he said it did.
At 07:35:16, the phone was picked up by a mast at Nangor Road which Mr Farrell said corresponded with Mr O'Reilly's account that he was at the Gym. At 08:12:57, the phone was picked up by mast at Chapelizod which he said accords with Mr O'Reilly's account that he was at work in Bluebell Industrial estate at this time.
He then analysed data from nine different calls.
The phone was picked up by various masts at Willsborough, Richardstown, Murphy's Quarry, two masts at Richardstown and a mast at Balheary.
Asked whether Mr O'Reilly's account that he travelled from his work in Bluebell Industrial Estate and went to the Broadstone Phibsborogh bus garage corresponds with analysis of his phone for the same time frame, he said: "It does not correspond."
He added: "They indeed give a different picture," in that they show a journey going towards North Co Dublin from Bluebell and then returning South from the same area.
Asked whether this was consistent with Mr O'Reilly's own account that he was in the Broadstone Phibsboro garage at this time, he said: "They are consistent with the description."
He said the phone being picked up by a mast in Chapelizod at 11:32:57 was consistent with Mr O'Reilly's own account, although he noted it was not similar to one of his accounts, which stated he didn't leave the garage until 11:30 that morning.
He said it would have been impossible for him to reach this mast so soon and that he must have left earlier.