https://www.bbc.com/news/articles/c84985w0w8voA teenage boy followed a 15-year-old girl for 45 minutes around a town centre before he stabbed her to death.
The boy has admitted killing Holly Newton (in Hexham, Northumberland), but denies he intended to harm her.
Jurors were told Holly was stabbed "many, many times" in an alleyway next to a pizza shop in January 2023.
The 17-year-old defendant, who was 16 at the time and cannot be identified, admitted manslaughter but denies murder.
Opening the trial, prosecutor David Brooke KC said the boy did "not dispute being responsible for stabbing Holly to death", but claimed his "mind went blank" during the attack.
Holly was stabbed in an alley at 5pm on 27 January 2023.
Her alleged murderer, who was known to her, had been "careful not to be seen" as he followed her for 45 minutes before the attack.
Passers-by and staff from the pizza shop heard Holly's screams and pulled the youth "forcibly" off her as he was "still stabbing her" with a kitchen knife he had brought from home.
Holly was taken to [hospital] but declared dead soon after, while the defendant was arrested at the scene.
She had 36 injuries, including 12 stab wounds and 19 caused by the slashing of a knife which broke during the attack.
The prosecutor said the assault lasted for at least a minute during which the "angry" boy stabbed Holly "many, many times".
His "intention was obvious", jurors were told.
The youth also denies wounding another teenage boy who was injured while trying to rescue Holly, the court heard, but has admitted illegal possession of a knife.
Mr Brooke told jurors the "violent death of a child" was "obviously shocking" and would "naturally arouse strong emotion".
