Jamie Fort, from Castle Bromwich, was 18 when he used a kitchen knife to stab his 57-year-old mother Patricia to death as his father and sister slept upstairs, Birmingham Crown Court heard.
Christopher Hotten QC, prosecuting, said Fort had called 999 in the early hours of July 28, 2008, from the family home in Lanchester Way telling the operator “I have killed my mother.”
When asked why he replied: “I can’t honestly say why I done it. Please just get there and deal with it before I go mad.”
Police found his mother lying in the living room. She later died in hospital due to blood loss.
Mr Hotten said experts had since found the teenager was suffering from a mental disorder called ‘dissociative disorder’ when he carried out the attack.
Now 22, Fort stood trial for murder in August 2010 but the prosecution accepted his plea to manslaughter on the grounds of diminished responsibility.
At his sentencing hearing at Birmingham Crown Court, Rachel Brand QC, defending, argued it would be “utterly wrong” to send Fort to prison.
But Judge William Davis QC said the “socially isolated” killer would still be a danger to the public if discharged from a hospital order and ruled Fort should remain in prison at least four years before being considered for parole.
“There is no doubt Jamie Fort killed his mother in a sustained and brutal attack with a kitchen knife,” he said.
“He had no reason to do that in terms of any dispute or argument with her.
“The reason he did what he did, there is no doubt, was because he was suffering from a significant mental disorder.
“The responsibility he had for his actions was very limited.”