A 14-year-old girl obsessed with serial killers prepared a "kill list" including the names of her friends, mother and brother before she attempted to murder her best friend by stabbing her at school, a court heard.
A jury was told the teenager, who cannot be named for legal reasons, lured her friend at the start of a school day to a quiet part of the grounds where she said she was going to give her a present.
But James Newton-Price QC, prosecuting, told Winchester Crown Court that when the defendant had got her friend alone, she asked her to close her eyes and hold out her hand before she pulled out a kitchen knife and stabbed her in the chest.
The girl escaped with a minor injury as she opened her eyes and managed to pull back as she saw the defendant lunge at her, the prosecutor said.
He told the jury that the defendant had researched fatal stab wounds in the early hours of the morning of the alleged attack at the Hampshire school on April 25.
Mr Newton-Price said: "The defendant was for a period of time obsessed with serial killers and school shootings and the notoriety that attaches to those who commit those crimes.
"She had even at one stage prepared what she described in her own words as a 'kill list' of those she didn't like at her school.
"She had even thought about how to kill her own mother and brother and she discussed how to do so in the two or three weeks leading up to an incident in which she stabbed her friend at school.
"It seems that she decided to kill her best friend. She had already researched online how to kill swiftly and effectively with a knife.
"She carried out further research about the position of the heart and the fatality of stab wounds in the early hours leading up the incident."
Mr Newton-Price said that the defendant had targeted the friend out of revenge for tampering with her Instagram and Tumblr social media profiles in the previous summer.
The defendant, who is now aged 15, denies charges of attempted murder and wounding with intent.