A 16-year-old boy was hit repeatedly with metal bars and bottles as he walked home from a New Year's Eve party, a court has heard.
Darren Carr, 35, his partner Nicola Faulds, 32, and a teenage boy and girl, who cannot be named because of their ages, deny murdering Bradley Whitfield.
He was walking home with three friends in Leicester when they were attacked by Mr Carr's group, the court heard.
The defendants said they were attacked and were protecting themselves.
Richard Latham QC, prosecuting, told Nottingham Crown Court that all of Mr Carr's group had been drinking when the attack happened on Fosse Road South.
When they started shouting abuse, Bradley's group responded and he was then repeatedly attacked.
Shortly after the attack Mr Carr, who used to live with Miss Faulds on Caldecote Road, Leicester, gave himself up. The court was told he said to police: "I'm scum. I have no excuse. I was drunk.
"I can't bring him back - he was just a kid. I was just protecting my family. I'm going to do life."
The prosecution claims all four defendants were involved in the attack and a vodka bottle used by Mr Carr was the murder weapon.
Witnesses said Nicola Faulds used a metal bar to hit Bradley while Mr Carr and the 15-year-old boy hit him repeatedly with bottles with such force that one smashed over his head.
Bradley bled to death from a 2.5in (6.4 cm) wound to his neck.
Mr Latham added: "The attack had been quick. It was over in perhaps a minute.
"But by the time Carr moved away from him, Bradley was gravely injured. Blood was pouring from his head. He collapsed with his head on the pavement, his legs on the road.
"At the point of the collapse, Carr ran back over and kicked him to the head."
The trial continues.
A 16-year-old boy was repeatedly struck walking from a New Year's Eve party, a court heard.