A man murdered his great nephew at a family party on a sprawling rural estate after he felt young revellers were not "showing enough respect", a court heard.
Raymond Dupree is accused of killing 20-year-old Ryan King by stabbing him with a wine glass, after the elder man complained about music being played by teenage girls in the early hours.
Mr King was said to have calmly stuck up for the 13 and 14-year-old girls who were at the gathering, held on August 20 last year to celebrate Mr King's pregnant mother's 40th birthday.
Witnesses said Dupree, 68, had been clenching a glass when he punched Mr King in the neck as the party began to quieten down at around 3am the following day. As Mr King fell to the floor clutching his wound, Dupree was said to have shown no remorse, saying: "I've done him," before leaving the estate and walking home. Dupree denies murder.
A terrified Mr King told shocked onlookers that he thought he was going to die, while friends frantically called for help. Mr King was taken to hospital but died later as a result of his injuries.
Speaking at the opening of the murder trial at Exeter Crown Court yesterday, prosecutor Simon Laws QC said Dupree "grossly over-reacted to a trivial dispute".
Mr Laws said: "There was simply no reason for Dupree to have used any force at all, still less the fatal force that he actually used.
"Mr King lost his life quite needlessly. His death was a product of Dupree's bad temper and his pride."
Exeter Crown Court heard Dupree and Mr King were among around 30 people celebrating Lisa Wilson's birthday at the luxury Snurridge Manor House, near South Molton in north Devon, which was owned by Dupree's sister.
Revellers said the party was "going well", with music, a buffet and karaoke.
But, as guests began to leave the party, witnesses said the atmosphere began to change.
Mr Laws told the court: "Dupree was behaving in a manner which was, at the very least, overbearing.
"Mr King intervened on behalf of a young girl that was bearing the brunt of the defendant's temper."
He said Mr King asked Dupree to leave the girl alone, prompting Dupree to say his relative should "respect his elders".
Dupree had apparently become angry that one girl had broken two glasses, and that the teenagers, who had been drinking, should have been in bed. Giving evidence, Mr King's friend Shane Thorne broke down in court as he recalled the attack.
He said there had been "a bit of a commotion about the music" at the party, adding: "Ryan followed Dupree into the kitchen to ask why he was doing it to (squabbling with) his own family. Dupree hit Ryan in his throat with a glass. Ryan was really shaken up. I walked up to him (Mr King) and saw the gash on his throat and all the blood."
The trial is expected to last until next week.