A teenager murdered a man in a nightclub minutes after being seen with a knife following a "trivial" altercation, a court has heard.
Ryan Passey, 24, was fatally injured in the early hours of 6 August inside Chicago's, Stourbridge, West Midlands.
Kobe Murray is accused of stabbing Mr Passey in the heart. Birmingham Crown Court was told he phoned his mother later telling her he had "messed up" and done something stupid.
The 19-year-old denies murder.
Mr Passey, an amateur footballer from Brierley Hill, died in hospital after the attack.
Prosecutor Phil Bradley QC said Mr Murray, of The Broadway, Dudley, was driven back to his home by a friend after allegedly showing him a blood-stained knife, which was dumped in undergrowth.
His father then drove him to West Bromwich police station, where he handed himself in, the court was told.
During a police interview, Mr Murray did not answer questions, the court heard, but presented a statement through his solicitor, claiming he had been attacked at the club.
"If I used a knife it was in self-defence. I do not recollect the exact circumstances due to being attacked and being intoxicated," the statement said.
But Mr Bradley told jurors: "There is no suggestion that Ryan Passey or anyone in his group was armed with a knife or other weapon.
"It is against this backdrop that Kobe Murray's use of a knife should be measured.
"You may think that taking a knife to an unarmed man falls well short of reasonable or proportionate."
The trial continues.