A British soldier who shot a teenager dead in Londonderry in 1972 will not be prosecuted, the Public Prosecution Service (PPS) said.
Daniel Hegarty, 15, was hit during Operation Motorman on July 31 1972, an army surge aimed at reclaiming "no go areas" in the city from the IRA.
The labourer was shot twice in the head by a soldier close to his home in Creggan. His cousin Christopher, 16, was shot in the head by the same soldier but survived.
An inquest into his death said they posed no risk but the PPS has decided to take no action.
Assistant director Michael Agnew said: "Our assessment remains that there is no reasonable prospect of proving to the criminal standard that Soldier B did not act in self-defence having formed a mistaken but honest belief that he was under imminent attack.
"In these circumstances there is no reasonable prospect of a conviction and test for prosecution is not met."
Soldier B had only been in the army around a year when the incident happened. He is now aged in his late 60s.
A review was launched following the 2011 inquest.
Mr Agnew said prosecutors had received further evidence from an expert witness who addressed the inquest but changed his evidence on hearing the account of the soldier. A second independent expert reached the same conclusion.
"The conclusions of both experts are such that they are not able to state that the ballistics evidence is inconsistent with the account provided by Soldier B of the circumstances in which he fired."
The ballistics evidence did not assist prosecutors in undermining the soldier's account, that his decision to fire was a split-second one and he felt under imminent attack. To launch a prosecution the PPS would have had to disprove his version of the facts beyond all reasonable doubt.
The prosecutor acknowledged that there was no objective justification for the shots fired by the soldier.
"Neither Daniel nor his cousins posed any threat to Soldier B or his colleagues.
"However, in a criminal trial the court will be required to assess the conduct of Soldier B in the context of the circumstances as he believed, or may have believed, them to be."