A 16-year-old Suffolk schoolboy accused of murdering his ex-girlfriend’s new boyfriend was suffering from Autism Spectrum Disorder (ASD) at the time of the killing, a court has heard.

Consultant psychiatrist Emma Went told a jury that the condition combined with other issues including depression, anxiety and symptoms of PTSD (Post Traumatic Stress Disorder) were “significant contributing factors” to his behaviour on the day of the attack on 16-year-old Harley Barfield.

Giving evidence at Ipswich Crown Court on Monday (October 30) Dr Went said the defendant’s ASD and lack of support for his mental health issues may have substantially impaired his ability to form a rational judgement and exercise self control on the day of Harley’s killing in Haverhill in January.

Dr Went, who was called by the defence to give evidence, said that during interviews with the defendant following the stabbing he had expressed regret and said of his decision to use the knife: “My body was doing it. It wasn't me. Adrenaline took over."

The court has previously heard that the boy’s parents had been worried about him having autistic traits and suicidal thoughts and he had been referred for a mental health and autism assessment.

However, although he was found to have significant autistic traits he hadn’t met “diagnostic requirements” at that stage, the court heard.

Following that assessment, the school had treated him as if he was autistic and made compromises about his behaviour and placed him on an additional needs register.

The court heard that the boy had a background of bad behaviour at school towards pupils and staff which had resulted in detention, suspension and exclusion.

He had also been the victim of several assaults including one which resulted in him suffering concussion and amnesia after being punched, kicked and stamped on by three youths.

The defendant, who can’t be named because of his age, has denied murdering Harley but has admitted manslaughter and possessing the knife used to kill him.

It has been alleged that he armed himself with a kitchen knife and lay in wait for Harley, who was going out with his former girlfriend, before confronting him in a “jealous rage” and trying to goad him into a fight.

Riel Karmy-Jones KC, prosecuting said the defendant and Harley, who she described as being in a “love triangle” had thrown punches at each other before the 16-year-old took a knife out of his pocket and stabbed Harley several times in a “frenzied” attack.

After the incident, the 16-year-old had run from the scene and had disposed of the knife.

Harley was airlifted to hospital where despite the efforts of doctors, he died two days after the stabbing on January 11 as a result of a fatal wound to his heart.

Miss Karmy-Jones alleged that the defendant was so obsessed with his ex girlfriend and jealous of her relationship with Harley that he murdered for her.

The trial continues.