A troubled teenager described himself as “evil” before he attacked 15-year-old Elianne Andam then threatened “do it again” while on remand for her murder, a court has heard.

On Wednesday, Hassan Sentamu, 18, declined to give evidence at his Old Bailey trial for killing 15-year-old Elianne outside the Whitgift Centre in Croydon, south London, on September 27 last year.

Jurors have heard that Sentamu, then aged 17, stabbed her in the neck with a kitchen knife after she stood up for his ex-girlfriend who wanted a teddy bear back.

It followed a catalogue of incidents of violent and aggressive behaviour by the defendant, who has been diagnosed with autism.

I look at my kitchen knives every night wondering if I should just end my misery now or live another day to see the ones I love. Life is hard and tough and I can break people physically and mentally

They included taking a knife to school, putting girls in a headlock, and expressing a desire to harm a cat and chop off its tail, according to agreed facts read out by prosecutor Alex Chalk KC.

On September 2 last year, Sentamu sent a message to a friend questioning whether he was “worth enough to live”, jurors heard.

He wrote: “Whenever you see me it’s never really me, it’s a persona I put on. The real me is evil, dark, and miserable.”

He confided that he did not think he would live past the age of 20, adding: “I look at my kitchen knives every night wondering if I should just end my misery now or live another day to see the ones I love. Life is hard and tough and I can break people physically and mentally.”

The month after Elianne’s death, Sentamu got into a row with a fellow inmate at Oakhill Secure Training Centre in Milton Keynes, jurors were told.

On being accused of killing girls, Sentamu responded: “I’ll do it again. I’ll do it to your mum.

“Do you want to end up like her, six feet under? I’ll do the same again.”

At the age of five, Uganda-born Sentamu came to the UK to live with his three sisters and mother who had fled domestic abuse.

When he was 11, he reported being physically abused and beaten with a metal pole after briefly attending boarding school in Uganda.

In November 2018, aged 12, Sentamu produced a knife in class, pointed it at his chest and told a teacher he wanted to kill himself, the court was told.

After being disarmed by teachers, he claimed he brought the knife to school to use in cooking lessons.

He received a police youth conditional caution for possession of a bladed article, the court heard.

Between 2019 and 2021, he lived in foster care after being left home alone and his mother said he was “beyond her control”.

He was permanently excluded from one school after he threatened another child with a knife during a farm trip because he felt he was being mocked.

In June 2019, he threatened to stab another student with a pair of scissors over perceived insults at a mainstream school in Croydon.

His foster carer reported an improvement in his behaviour, although his temper would “quickly escalate”.

Mr Chalk told jurors: “When he did not get his way he would threaten to harm the cat or chop off its tail. He expressed a wish to kill himself while living with her and on once occasion drank shower gel and attempted to get a knife from the kitchen.”

On two occasions in December 2019, Sentamu placed female students in a headlock, leaving marks on one girl’s neck.

The following year, he was placed in a school for students with special education needs but continued to struggle with his temper, jurors heard.

In October 2022, his mother called police to report he had become angry, locked himself in his room and covered the walls with washing up liquid.

Within an hour and a half of stabbing Elianne, Sentamu was arrested as he made his way home to New Addington on a bus.

In a police interview, he was asked if there was anything he would like to say to Elianne’s family and answered “no”, the court heard.

Two months after her death, an ambulance was called to Oakhill after reports that Sentamu had ingested the contents of a chemically activated ice pack, the court was told.

Staff also recovered a notebook in which he was “counting down to his own suicide”, jurors heard.

In April, he made a complaint against a female staff member saying he was “very angry and felt like hitting her”.

Sentamu, who was studying sports science at Croydon College, has admitted manslaughter but denies Elianne’s murder on the basis of “loss of control” because he has autism.

He denies a charge of having a blade, claiming he had a “lawful reason” for carrying it.

Mrs Justice Cheema-Grubb adjourned the trial until January 6.