Leo Norney, 17, was killed in disputed circumstances in the Turf Lodge area in September 1975.
Soldiers from the Black Watch regiment said he was a gunman who had opened fire on them.
But people in the area said he was an innocent victim of an unprovoked attack.
The original inquest in 1976 returned an open verdict.
I recall him telling me that we were going to waste somebody tonight
On Monday an Army veteran, referred to as M2, told an inquest in Banbridge that he had falsified his previous statements and that his patrol had not been fired on the day Leo was killed.
The witness said he wanted Leo’s family to know the truth about what happened more than 40 years ago.
The bulk of his evidence centred around the actions of Corporal John Ross MacKay, who died in 2015.
M2 said that after an attack on the soldiers’ base in which no one was injured, he returned to his room.
Two other soldiers, referred to as M1 and M3, were there with Cpl MacKay.
In a statement to the inquest, read out by counsel for the coroner Ian Skelt, M2 said: “I recall him telling me that we were going to waste somebody tonight.
“I can’t recall his precise language, but it was words to that effect. I recall he used the word waste.
“I immediately responded by saying I would not be involved in what he was suggesting and that he must be mad.”
In the statement, M2 said he did not recall Cpl MacKay saying who the target would be or where or how it would happen.
He said M1 and M3 were in earshot of the exchange.
I thought he was maybe sounding off. I didn't think anyone would be capable of doing that
Asked by Mr Skelt to explain what he understood Cpl MacKay to mean, M2 said: “I took it he was going to harm somebody, maybe kill them.”
He was also asked if he took the comments seriously or just saw it as bragging, and said: “I don’t know really, I didn’t think anyone would do that.”
He said Cpl MacKay was in a “foul mood”.
“I took it that he meant that, but afterwards I thought he was maybe sounding off. I didn’t think anyone would be capable of doing that.”
M2’s statement described the events of the patrol before the incident in which Leo was killed.
The witness described his position at a security fence in west Belfast.
He described glancing over to Cpl MacKay and seeing him fire his rifle towards an area known as Shepherd’s Path.
M2 said Cpl MacKay fired two quick shots, followed by several further shots.
He said he did not recall hearing or seeing any other gunshots before Cpl MacKay fired his rounds.
He also said he saw M1 fire a single round of his rifle at a Mini car parked close by, but added he could not recall where the car was struck.
He had a lot of influence. I wasn't prepared to put myself in harm's way. I just went along with what he told me to do
“I believe the shot fired by M1 occurred very soon after the shots fired by Cpl MacKay,” M2 told the inquest in his statement.
He recalled being ordered to take cover at waste ground and hearing a person groaning from the direction of Shepherd’s Path.
“I looked towards the area the noise came from and saw a soldier who I recall being Cpl MacKay standing beside or on Shepherd’s Path.”
He said he saw a soldier, who he believed was Cpl MacKay, point his rifle towards the ground and fire one round.
He told the hearing he did not see a body from his position, but believed the bullet struck the concrete path.
He also recalled hearing Cpl MacKay kicking an unseen object on the ground.
“I recall hearing the thud of something being kicked,” he said.
Later, he described the arrival of other soldiers at the scene and accidentally discharging his rifle.
Asked by Mr Skelt why he gave a false narrative of events, he said he was scared of Cpl MacKay.
“I had just seen what I had seen and I wasn’t going to put myself in a position of going out on patrol with someone who had did that.
“If he had done that to somebody that he didn’t know, what was the next thing?
“He had a lot of influence. I wasn’t prepared to put myself in harm’s way. I just went along with what he told me to do.”
He described MacKay in his statement as a “violent and unpredictable person”.
M2 told the inquest that before now, he had been scared to tell the truth, but added: “Leo Norney’s family deserve to know the truth about how he died.”
He was questioned later by Mark Mulholland, counsel for M1, about his lack of recall of previous statements he had given over the years about the incident, as well as his history of mental health problems, and said his most recent statement was true.
Questioned by Fiona Doherty, counsel for Leo’s family, he said: “If I could turn the clock back, it would not have happened.
“I am deeply sorry Leo Norney died and his family had to suffer.”