The mutilated body of teenage murder victim David McIlwaine lay in a mortuary "practically decapitated", the High Court has heard.
A former soldier also compared the condition of his remains to sights he witnessed during service in war-torn Kosovo.
Robert Thornbury gave his assessment during a negligence case brought by David's uncle over being allegedly forced to identify the body against his will.
Alan Steele is suing the Chief Constable for psychological injuries he says were inflicted by his task in the morgue.
Mr Steele's 18-year-old nephew was stabbed to death along with Andrew Robb, 19, in February 2000. Their bodies were then dumped by a road near Tandragee, Co Armagh.
Mr Steele has claimed officers did not care about making him identify the body because they wrongly believed David was a member of the Loyalist Volunteer Force.
In evidence to support his case, Mr Thornbury told the court on Friday he was also at the mortuary to identify the body of his own nephew, Andrew Robb.
Mr Thornbury said he offered to go in with Mr Steele because he was crying, shaking and saying he could not go through with it.
"I also told him I was a serving soldier, only home from Kosovo. I saw lots of things out there, but what I saw in there was terrible."
He claimed a sheet had been pulled up to just below David's shoulders, and disputed police assertions that the worst of the facial injuries were covered.
"There was a large, gaping wound on the left-hand side of his face," Mr Thornbury said.
"I could see that David had a very, very deep wound to his throat. He was practically decapitated, you could see right into his throat."
During cross-examination, David Ringland QC, for the police, said the senior detective at the scene had no recollection of Mr Thornbury being present at the identification of either victim.
But he replied: "If I can't have seen those wounds how could I have known that the deep slash was on the left hand side of the face?"
Also giving evidence was former DUP MLA Paul Berry, who met the victim's uncle at the morgue.
He recalled Mr Steele saying he was being forced or pressurised into carrying out the identification because the parents could not be contacted.
David's father, Paul McIlwaine, told the court how he and his wife Gail learned of his murder on their return from a trip to Belfast.
Following two days of evidence, Mr Ringland contended that Mr Steele qualified as neither a primary or secondary victim.
He also argued that police have an immunity from any duty of care obligations when investigating a criminal act.
Lord Justice Coghlin, who is hearing the action, reserved his decision on the application.
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