On that day Porritt, who was estranged from his parents and did not live with them, told his mother he planned to sue for injustices he experienced as a child.

She demanded he leave the house.

Mrs Porritt then "tragically reinforced her demand by picking up and brandishing a sharp knife", Justice Higgins said today.

Porritt was criminally negligent because he followed her upstairs when she went to call the police and "became trapped in the bedroom".

"His mother, not unnaturally, was seriously alarmed ... and flashed at him with the knife."

In a panicked attempt to leave the room, Porritt then fatally stabbed his mother "negligently unmindful of his then possession of the knife".

The stress of being charged with his mother's murder and being remanded in custody had led to Porritt developing a schizophrenia-type disorder, Justice Higgins said.

The 24-year-old has expressed genuine remorse for his actions, the court heard earlier this year. Porritt told his probation and parole officer: "I should have left the house when she (his mother) asked me to. I didn't. I'm responsible."

His mother's death was a tragedy because she had been trying to make amends and they "could have made peace".

Porritt has been placed under an involuntary mental health treatment order and prescribed anti-psychotic medication.

He has also been placed on a good behaviour order for four years.