One of the men accused of killing Mary-Ann Leneghan has now admitted murdering her, attempting to murder her friend and kidnapping them both.
Mary-Ann was raped and tortured before her death
Michael Johnson, 19, of Southfields, south-west London, is one of six men standing trial for the abduction, rape and murder of the 16-year-old.
Johnson continues to deny charges of rape and causing grievous bodily harm with intent.
Mary-Ann's body was found in Prospect Park in Reading, Berks, on 7 May 2005.
Her friend survived being shot in the head.
Mary-Ann was abducted with her friend, now 19, who cannot be named for legal reasons, and taken to a hotel room where they were both allegedly abused before being taken out to die, Reading Crown Court has heard.
Moments before Johnson's admission on Thursday, the judge - Mr Justice Penry-Davey - said he would be instructing the jury in due course to acquit him of causing grievous bodily harm on both girls and ask them to consider a separate charge of causing actual bodily harm on Mary-Ann's friend.
The court has been told that Johnson called his social worker Michelle Martin on the day of the murder and hinted at responsibility.
He later told her that he had gone to Reading as two girls had "set a man up to be robbed" and at a car park they had put the girls into the boot of a car and driven them to a hotel.
He told her that the girls had later been put back into the car and driven to the park.
Johnson then said: "Man whose beef it was had the knife but he couldn't do it so he gave me the knife and I was saying to the man 'it's your beef, you do it, it's your beef'.
"It's like he couldn't do it so I stabbed her and I shot the other one."
Johnson is on trial alongside Adrian Thomas, of Battersea, south London; 23-year-old Joshua Morally, of Balham, south London; Jamaile Morally, 22, of Balham; Llewellyn Adams, 24, of Balham; and Indrit Krasniqi, 18, of Chiswick, west London.
Joshua Morally has admitted two counts of kidnap but denies murder, attempted murder, rape and causing grievous bodily harm with intent.
The other four deny all the charges.
The trial was adjourned until Friday.