The trial of three alleged dissident republicans has heard there is no "independent verification" of MI5 audio recordings made of secret conversations in a Co Armagh park.
Belfast Crown Court had previously heard that MI5 planted covert listening devices at Demesne Park, Lurgan, to eavesdrop on alleged conversations between Colin Duffy (52), Henry Joseph Fitzsimons (51) and Alex McCrory (58).
Codenamed 'Operation Contraction', the covert listening operation was mounted in the wake of a gun attack by dissident republicans on a three vehicle police convoy as it was travelling along the Crumlin Road in north Belfast on December 5, 2013. As well as audio recordings, MI5 had also placed cameras in the Lurgan park to video record their alleged meetings, which was codenamed 'Operation Succinctness'.
The court has heard that the Lurgan audio recordings were downloaded from the listening devices onto a USB memory stick before being uploaded onto a computer system called 'Marshbrook' at MI5's headquarters in London.
An MI5 officer, known only by the cypher PIN 4039, gave his evidence to the court from behind a curtain at the non-jury Diplock-style trial being heard by judge Mr Justice O'Hara.
He confirmed to the court that the Marshbrook computer system had now been "decommissioned" and had since been replaced by another computer system.
The agent was questioned about the transfer of data from the listening devices to the USB stick and uploaded onto the 'Marshbrook' computer system.
Defence counsel Mark Mulholland QC put it to PIN 4039: "Do you agree that there is no independent verification of the (Lurgan) audio tapes apart from your evidence here today?"
The witness replied: "I agree, My Lord, that aspect of how the data was transferred from the USB device to the computer system is by my oral evidence. It would appear we are relying on my evidence."
Duffy, Fitzsimons and McCrory, whose addresses can't be given at this time, deny preparing and directing terrorism, and membership or professing to be members of the IRA.
Fitzsimons and McCrory are also charged with - and deny - attempting to murder police in the convoy, and having possession of the two AK47 assault rifles and ammunition used in the 2013 attack.
Two gunmen armed with AK47 assault rifles fired 14 high velocity rounds at the police vehicles close to Holy Cross Church in Ardoyne.