In the first day of his re-trial over the killing, the 31-year-old paratrooper relived the frantic moments that led to the death of 18-year-old Karen Reilly. At one point he held an imaginary rifle in his arms to portray to the court how he fired at the car.
The paratrooper, who was jailed for life but freed on licence in 1995, said he and his patrol had been warned that evening of the likelihood of terrorist attack before they set up a roadblock on the Glen Road.
He described how "bloody frightened" he had been on patrol in Northern Ireland especially during periods of "high terrorist activity".
The shots he fired were the first he had discharged in his five months of active service. His only experience of weaponry had been during training.
Clegg said he had been certain that the car had hit a colleague and described the moment when he opened fire.
"I thought, 'Bloody hell, it has hit him'. When it had done that it came across to my side of the road. It was coming directly across to my position," he said.
The incident was over "literally in a flash".
"You are bloody frightened - in this environment, unfortunately, with high terrorist activity and we had been given a briefing by intelligence that it is imminent that PIRA (Provisional IRA) are going to attack," he said.
His defence counsel, William Clegg QC, added that the paratrooper and his unit had not been told they were part of an operation to deter joy- riders, as that might have resulted in them lowering their guard.
He also said Private Clegg was acting in defence of a fellow soldier. "There was a genuine and reasonably held fear in the mind of Private Clegg that his patrol that night could be the target for terrorist attack," he said.
"The anticipation of terrorist attack had been intensified at an intelligence briefing given to this patrol that very evening," said the QC. There was also the question of Private Clegg's so-called Yellow Card training.
"We were told there were situations on the yellow card that would permit you, always depending on the circumstances, to open fire, and that if you acted in accordance with the rules and regulations of this yellow card you were bound by law to be OK," he explained.
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