Gardaí traced all calls, texts and locations of 13 mobile phones they believe were used by a gang on the day they shot a man dead outside his home, a trial at the Central Criminal Court heard today.

The operation was revealed during the trial of Gary Flynn (aged 31), of Rossfield Drive in Tallaght. Mr Flynn has pleaded not guilty to the murder of Seamus 'Shay' O'Byrne on March 13, 2009 at Tymon Park North in Tallaght.

Senior crime and policing analyst Sarah Skedd worked with gardaí to make sense of information gathered from more than a dozen mobile phones.

She told prosecuting counsel Alex Owens SC that she discovered dozens of texts and calls made between the various phones in the run-up to the shooting and afterwards.

One of the texts was from a phone identified as belonging to a man gardaí suspected of involvement, Eugene Cullen.

Sent shortly after 7am the day before Mr O'Byrne was fatally shot, it read: "You up mate".

The phone that received the message was found in the garden where Mr O'Byrne was shot and is linked to another man who has already been convicted, named Garrett O'Brien.

Defence counsel Giollaíosa Ó Lideadha earlier told the court that it is the prosecution's case that Mr O'Brien was the shooter.

Mr O'Brien's phone responded within two minutes: "Yeah. Be leaving in a few mins."

Ms Skedd said that she had prepared a series of charts to explain how the different phones interacted with one another over the three days leading up to the shooting on the evening of March 13m 2009.

Her evidence will continue tomorrow.

Brendan McKenna of Vilicom Engineering told Mr Owens that he analysed the locations of dozens of mobile phone masts that were linked to some of the phones.

A phone that was seized when Garrett O'Brien was arrested by Detective Sergeant Thomas Doyle four days after the shooting, had interacted with masts located from Bray, Co Wicklow, to Ballymount Industrial Estate in Dublin 12.

Another phone that was found in a Nissan Primera car that gardaí suspect was used by the alleged gang, was traced to the Coolock area about one hour after the shooting.

The trial previously heard from Liam Fleury of the Forensic Science Laboratory who told Mr Owens that fingerprints he lifted from that same Primera matched Mr Flynn's.

The trial continues before Justice Patrick McCarthy and a jury of nine men and three women tomorrow.