A 15-year-old girl was fatally stabbed while standing up for a friend who had wanted to get back her teddy bear from her ex-boyfriend, a court has heard.

Elianne Andam was attacked by Hassan Sentamu, who was 17 at the time, outside the Whitgift shopping centre in Croydon, south London, in September 2023.

Mr Sentamu chased after Elianne, cornering her and stabbing her repeatedly with a kitchen knife, before running away and disposing of the weapon, the Old Bailey heard.

He previously pleaded guilty to manslaughter but is on trial charged with murder, which he denies.

Prosecutor Alex Chalk KC said the defendant, now 18, did not deny wielding the knife and causing Elianne’s death but had pleaded not guilty to murder on the basis that his responsibility was diminished due to his autism.

Mr Sentamu also denies illegal possession of a blade, claiming he had a “lawful reason” for carrying it.

Opening the trial, the prosecution told the court Elianne had gone along with her friend, and a group of girls, to meet the defendant in a car park on the morning of 27 September.

Her friend and Mr Sentamu, who had split up 10 days earlier, had planned to exchange their belongings.

Mr Chalk told the jury that Mr Sentamu had turned up empty handed, and that Elianne was “aggrieved on her friend’s behalf”.

She seized the plastic bag her friend had given the defendant in “a gesture of solidarity… that cost Elianne her life”, Mr Chalk said.

“The defendant chased after her, cornered her and used the kitchen knife to stab her repeatedly,” the prosecutor told the court.

“He drove the knife 12cm into her neck, severing the carotid artery and causing injuries that were unsurvivable.”

CCTV footage captured the attack, and Mr Sentamu running from the scene and disposing of the knife. He was arrested at a bus stop near his home less than 90 minutes after the killing.

The prosecution’s case is that the catalyst for the attack was “white-hot anger, at having been disrespected in public”.

Jurors were told they would have to decide whether the defendant’s autism offered him a defence in law, and whether it provided an explanation for his actions.

Mr Chalk said the prosecution acknowledged “with compassion” the challenges posed by autism but he told the court that the condition did not amount to an “excuse, justification or defence” for Elianne’s murder.

Sentamu had a “short fuse” and on the day of the killing, he came to the end of it, jurors heard.

Mr Chalk said: “His calculated decision to bring a knife to the scene meant that the consequences of that outburst for Elianne and her family were utterly devastating.”

The trial continues.