A man jumped into the dock in a court to confront the defendant who had previously stabbed him in the back.
Connolly Mellon, 20, was dragged away by security staff as he tried to attack 22-year-old Luke Batchelor just before Batchelor was jailed.
Batchelor had stabbed Mr Mellon in the back twice at a student Halloween party in Ditchling Road, Brighton, in the early hours of Sunday 31 October last year.
He plunged a knife into Mr Mellon’s back without warning because Mr Mellon would not share some cannabis with him, the court was told.
Mr Mellon suffered a punctured lung in the attack and bled heavily from his knife wounds.
Batchelor, meanwhile, fled the student flat.
The defendant, of Inwood Crescent, Brighton, pleaded guilty to wounding Mr Mellon with intent to cause grievous bodily harm (GBH).
He was jailed by Judge Simon Coltart who imposed an indeterminate sentence and told him that he would serve a minimum of three years.