Two teenagers have been found guilty of murdering 17-year-old Jodie Chesney in a park in east London.
Jodie was stabbed in the back in a case of mistaken identity as she socialised with friends in Harold Hill on 1 March.
Drug dealer Svenson Ong-a-Kwie, 19, and a 17-year-old boy were both convicted of murder following an eight-week trial at the Old Bailey.
Manuel Petrovic, 20, of Romford, and a 16-year-old boy were both cleared of murder and manslaughter.
The jury spent less than six hours deliberating their verdicts on all four defendants.
Judge Wendy Joseph QC said Ong-a-Kwie and the 17-year-old boy, who cannot be named for legal reasons, would be sentenced on 18 November.
Following the guilty verdicts, Det Ch Insp Dave Whellams, of Scotland Yard, said the murder of "girl next door" Jodie had "shocked a nation".
He added: "It could have been anybody's daughter. She was a very nice girl, she had a small circle of friends, she did well at school, worked in the community.
"They have gone there purposefully to stab somebody and they have not cared who they stabbed. They stabbed a 17-year-old girl in the back for no reason."
Throughout the trial it was never disputed that Ong-a-Kwie and the teenager were the two people who went into Amy's Park on the night Jodie was stabbed.
The pair blamed each other for the stabbing, while Ong-a-Kwie admitted burning his clothes with a cigarette lighter.
Jurors heard Jodie had her back to her attackers and the knife almost passed right through her body.
After being stabbed the teenager screamed and fell into the arms of her boyfriend Eddie Coyle, the court was told.
Frantic efforts were made to save her but she was pronounced dead in a petrol station in Gants Hill about an hour later.
Following the verdict, Peter Chesney said his daughter's murder had "destroyed my life".
"I have no idea how I am going to continue with my life or even come to terms with the loss," he said.
Jodie's sister Lucy wrote in a victim impact statement that she had been "dreading my life rather than looking forward to it" following the 17-year-old's death.
"Jodie was not only my sister she was my best friend. Losing her is like losing half of myself."
She added that she was now "anxious about everything" as "if someone as good and pure as Jodie could be murdered, it could happen to anyone and I spend everywhere I go looking over my shoulder because of it".
Prosecutor Crispin Aylett QC told the jury Jodie was "a victim of a brutal act of unprovoked violence".
He described the girl's death as "another example" of the "terrible consequences of the carrying and using of knives".
"It seems every day now in our city another young life is lost to a knife," he said.
During his evidence, Mr Petrovic admitted driving the group to Harold Hill but denied any knowledge of what happened in Amy's Park.
He told jurors he was "glad he was arrested because he had nothing to hide".