Lyle Tulloch had 13 stab wounds
A 15-year-old was killed at a birthday party following a row over a mobile phone, the Old Bailey has heard.
Lyle Tulloch, from Peckham, was stabbed 13 times in a stairwell at Newall House, Borough, south London, on 3 May.
Damien Sobowale, 18, of Gypsy Hill, south-east London and a 17-year-old youth from Deptford, who cannot be named, both deny Lyle's murder.
The defendants had confronted Lyle over Sobowale's mobile phone which went missing at the party, the court heard.
Lyle was attending a friend's 15th birthday party when the incident took place.
Row over hug
Sobowale had gatecrashed the party with the other youth and a girl but when he saw the girl hug Lyle he confronted the boy.
David Waters QC, prosecuting, said others intervened and Sobowale appeared to have "forgotten the incident".
Later in the evening Sobowale rounded up and searched some partygoers when his phone went missing after he said he leant it to Lyle's friend.
The court heard the defendants dragged Lyle to a corner and attacked him.
Mr Waters said: "Sobowale could be seen to have the knife, now in his hand, and not surprisingly Lyle Tulloch was backing away.
"He suffered 13 separate stab wounds. Two passed through his right lung and another entered the right ventricle of his heart."
Mr Waters added that when Lyle's friend tried to distract his attackers shouting 'I am the one with the phone' a knife-wielding Sobowale tried to stab him.
The youth jumped from the the second floor balcony on to a ledge to escape.
"He was sufficiently terrified to jump over the balcony from the second floor in order to escape," Mr Waters told the jury.
Mr Waters told the court that partygoers saw the 17-year-old accused stab Lyle in the leg and saw a knife dripping with blood in his hands.
Tests showed that the blood found on Sobowale's trainers and a hooded top belonging to the other defendant matched that of the victim, the court heard.
Both defendants maintain they left the party before the attack on Lyle.
The trial continues.