The Morris tribunal is to investigate allegations of Garda involvement in an arson attack on a telecommunications mast at Ardara six years ago.
Continuing his opening statement, Mr Peter Charleton SC, for the tribunal, said the incident raised a number of questions, including the decision by a superintendent to issue warrants for the arrests of local residents Mr Hugh Diver and his late brother, Anthony.
He also said the role of Sgt John White in the investigation would have to be examined.
Mr Hugh Diver has accused the garda in question of planting poitín on his premises as well as trying to frame him for the arson attack.
Sgt White, who was subsequently promoted to the rank of detective sergeant, was arrested in March 2000 on foot of the Carty inquiry. He has denied taking part in any criminal or illegal activity.
Mr Charleton noted the Ardara site was the subject of a lengthy protest by local residents who were concerned about the mast's potential health effects. In December 1995, a large force of gardaí had to be called in to protect employees of a cable company working there.
The site was subsequently subjected to vandalism, including an arson attach which cost an estimated £55,250 in criminal damage. In November 1996, a "crude" explosives device was also found at the site.
Mr Charleton said the device was "nothing more than an assembly of fireworks", and further noted gardaí had seized a quantity of fireworks in Glenties two months earlier. However, "as to whether any of these were similar to the fireworks found in the device on the mast at Ardara it cannot now be said because they were later burned in a disused quarry in Glenties".
The tribunal heard the device was brought to Glenties Garda station after it was found. There, it was taken apart and examined. Garda John Kilbane said he recalled Sgt White taking a spoonful of powder which had been removed from the device and bringing it to the back yard.
"He left the spoon of powder on the steps outside the back door and attempted to light the powder with the matches I had given him," said Garda Kilbane.
Mr Charleton said it needed to be questioned "how it could be proper" for a non-technical member of the Garda to treat an exhibit in the way described, if indeed it occurred.