A ST ALBANS teenager who killed a mentally ill neighbour to save his mother from attack was fully exonerated in an inquest today.

After a day-long hearing, coroner Edward Thomas ruled that Jonathan London, 46, was lawfully killed by James Killen, 18, on the morning of April 30.

He also recorded in a narrative verdict that James' mother Sandra Crawford, 53, died eight days later in Addenbrooke's Hospital, Cambridge, from stab wounds inflicted by a person suffering severe mental illness.

He told both families at Hatfield Coroner's Court: "Listening today must have been really hard for all of you.

"I am particularly sorry for you, James - if this was me when I was your age and it was my mum, I can't imagine what it would have been like."

The inquest heard that James, a pupil of Sandringham School, had been drying his hair in his bedroom in his family home in Sherwood Avenue when he heard his mother screaming.

He did not give evidence, but the inquest heard his tearful and dramatic statement to police after his arrest for attempted murder.

He told officers: "I saw my mum on the floor - a man was on top of her.

"I saw him punch her, shouting 'Die, die."

"There was a pool of blood. I jumped on his back and started to scream at him.

"Then I realised he had a knife - I saw him stab my mum.

"I tried to get hold of the knife.

"He started to point the knife towards me."

The teenager ran to get a second knife from the kitchen and returned to the hallway where his neighbour continued to attack his mother.

His statement continued: "He was just too strong.

"I stabbed him a few times, but he kept going at my mum.

"She was in real danger. I stabbed him again.

"Mum got up and ran outside.

"The phone had been disconnected, so I ran upstairs to get my mobile.

"The man had collapsed on the floor."

Detective Inspector John Arthur said James was soon released as his statement was consistent, and supported by forensic evidence.

It appeared that Mr London had first confronted Mrs Crawford in the kitchen before attacking her with a knife he found there.

He was found dead at the scene with 16 stab wounds, while Mrs Crawford was taken from the garden, where James frantically tried to revive her, to the Cambridge hospital by air ambulance.

The inquest heard how Mr London, formerly a lab assistant at the University of Hertfordshire, had developed psychiatric symptoms, probably a reaction to his treatment for epilepsy.

The day before, his mother and brother Rodger took him to Watford General Hospital, where he had blood tests and a psychiatric assessment.

Dr Seshni Moodliar said he was seriously deluded, but calm and without any sign of aggression.

Intensely cross-examined by barristers for both families, she said there was no reason not to refer the patient for home treatment by a community mental health team.

She agreed, however, that she might have admitted Mr London for compulsory treatment had she known how his behaviour deteriorated as soon as he got to the hospital car park.

His brother Roger went back to reception and asked for help, but clinical staff were not informed.

The brothers walked back to St Albans, and the next morning the community mental health team tried in vain to contact the patient, not knowing of the gruesome events in Sherwood Avenue.

Dr Thomas said the decision to treat at home was understandable as the patient had a supportive family, but he would write to hospital bosses about the staff communication failure.

Mr London's family did not want to comment after the inquest, but Mrs Crawford's relatives said: "We hope and pray that out of these tragic events some lessons will have been learnt and that other families will not have to endure the same trauma as we have."