But the trial judge, Mr O’Hara, said he was satisfied beyond a reasonable doubt that Holden was guilty of manslaughter by gross negligence.
He said Holden should have appreciated the consequences of his actions from the moment he pulled the trigger.
Judge O’Hara said the weapon, controlled by David Holden, was “lethal in the extreme”.
He told Belfast Crown Court: “It was suggested on his behalf that it was not exceptionally bad or reprehensible to assume that the gun had not been cocked. I fundamentally disagree.
“In my estimation this was the ultimate ‘take no risk’ position because the risk of disaster was too great.
“The defendant should have appreciated at the moment he pulled the trigger that if the gun was fired, fatal consequences might follow.
“This is not something that becomes apparent in hindsight.
“The defendant took an extreme risk without cause in circumstances in which he was neither under pressure nor danger.
“In light of the foregoing, I find the defendant guilty of the gross negligence murder of Aidan McKinsby.”
Holden is a former Grenadier Guardsman from England whose address is given in court documents as follows: c/o Chancery House, Victoria Street, Belfast.
The case was heard in Diblock format without a jury hearing.
Holden’s supporters gathered outside the court each day the trial was held.
The trial has continued amid ongoing controversy over the government’s plans to deal with Northern Ireland’s turbulent past.
The Northern Ireland Troubles (Inheritance and Reconciliation) Bill proposals offer an effective amnesty to those suspected of killings during the conflict, if they agree to cooperate with a new body, known as the Independent Commission on Reconciliation and Information Recovery (Icrir).
The bill also bans future civil cases and investigations of unrest crimes.
The Holden case is one of a series of high-profile trials of veterans prosecuted in Northern Ireland in recent years.