Hassan Sentamu struck the 15-year-old with a kitchen knife as he refused to return items owned by her friend who he had just split from, the Old Bailey heard.
When Elianne grabbed a bag of his clothes in solidarity with the girl, Sentamu chased after her in South London and repeatedly stabbed her, the jury was told.
As she collapsed by Croydon's Whitgift Centre, Sentamu - then 17 - fled and dumped the knife nearby, jurors were told.
He was arrested soon after when police stopped a bus near his home in New Addington.
Sentamu, who was studying sports science, admits manslaughter but denies murder, on the basis of "loss of control" as he has autism.
He also claims he had a "lawful reason" for carrying the knife in September 2023.
In a video interview played in court yesterday, his ex-girlfriend said she realised that something was wrong when he turned up to swan belongings in a mask and gloves.
This story is from the {{IssueName}} edition of {{MagazineName}}.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber ? Sign In
This story is from the {{IssueName}} edition of {{MagazineName}}.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber? Sign In
All change at the back once again for Gunners
BUT MIKEL SHRUGS OFF EXPANDING INJURY LIST
Carse driving towards star role in England's Ashes plans
SEAMER'S ON FAST TRACK
STOP MOANING AND ENJOY LONG TRIPS
Pollard gives positive spin
I'm the victim, claims pub row boss
A COUPLE accused of attacking the owners of an upmarket pub when they were refused drinks after hours have claimed they were acting in self-defence as the victims of a \"lynch mob\", a court heard.
'My secret for a long life? A glass of chardonnay a day!'
D-Day nursing heroine Jean marks 103 with cake - and her tipple
Bake Off with a soap flavour
A BATTLE of the soaps is being cooked up in the Bake Off tent this Christmas as the show returns for its yuletide special.
Homeless rises to ‘at least' 354k on a given day
SOME 354,016 people were estimated to be homeless in England on a given night this year, research from Shelter claims.
Arrested after applying for 13 passports
A MIGRANT suspected of organised crime gang links has been arrested in a Home Office swoop after he applied for 13 passports for foreign children.
Murder probe after attack on John, 82
A MURDER investigation has been launched after a \"world-renowned craftsman\" died after he was attacked in his home.
'Killed son dies in my mind each day'
THE mum of a boy murdered in an unprovoked stabbing says she loses her son \"every single day\".
