A pub-goer slashed the neck of a 21-year-old man in an act of “pitiless savagery” then went on the run for more than three years, a court has heard.
Shane O’Brien, 31, fatally stabbed Josh Hanson after a brief conversation in RE Bar in Hillingdon, west London, in October 2015, jurors were told.
Prosecutor Mark Heywood QC told jurors what took place was “sudden and shocking”.
Mr O’Brien denies murdering Mr Hanson and is on trial at the Old Bailey.
The pair had never met before their paths crossed for a matter of seconds in the bar, jurors were told.
The prosecutor told the court Mr O’Brien accepted he used the blade to cause Mr Hanson’s death but says he is not “criminally responsible” because he did not mean for it to happen.
Earlier on 10 Oct 2015, Mr Hanson had gone to hospital with his girlfriend after her father suffered a suspected heart attack.
They then met up with his cousin and a small group of friends for a drink in RE Bar.
About an hour later, Mr O’Brien arrived with three other men, Mr Heywood said.
Mr O’Brien was shown in CCTV footage to “surreptitiously” reach for his blade in the pocket of his jacket, the court heard.
Mr Heywood said: “He suddenly raised his right hand, holding the blade, to a level above the head of Josh Hanson.
“He then brought the blade down in a sweeping, slashing motion, aimed at and striking the exposed skin of John Hanson’s ear, neck and chest.”
Mr Heywood said the stabbing was “catastrophic” and left a 37cm long gaping incised wound from the victim’s left ear to right chest.
Mr O’Brien fled to a caravan park in Camber Sands, East Sussex, but was recognised by pub staff at the nearby Camber Castle following a Facebook police appeal, jurors were told.
Before he could be apprehended, Mr O’Brien was flown in a private plane from Biggin Hill airport to the Netherlands, the court heard.
Jurors were told despite an international manhunt, O’Brien evaded authorities for years.
He was arrested in Romania on 23 March and extradited to the UK.
The trial continues.