A TEACHER'S son brutally murdered his girlfriend after being driven mad by ten years of smoking cannabis, a court heard today.
Teacher's son Marc Middlebrook ignored repeated warnings to quit the drug when he stabbed Stephanie Barton 15 times as she lay naked in his bed.
Psychotic Middlebrook, 27, had become convinced she was part of a plot to kill him and later said he “wanted to put her out of her misery”.
He has admitted manslaughter on the grounds of diminished responsibility, claiming he was suffering from mental health issues at the time.
But prosecutors say he made his problems worse by “stubbornly” persisting in his use of cannabis – despite doctors advising him to stop.
William Harbage QC, prosecuting, told Middlebrook’s murder trial at Lincoln Crown Court: “If it was not cannabis we would not all be here.
"You will hear about his odd behaviour. It included the paranoid belief that his life was under threat by a group of people intent on killing him.
"We say the main cause of this odd behaviour is his long-standing abuse of cannabis smoking, which we say is entirely self-induced.”
A jury heard Middlebrook had smoked cannabis since the age of 16 or 17, increasing his use after meeting accountancy student Miss Barton, 32.
He had cut down on his habit shortly before the killing but was nonetheless still smoking the drug “right up to her death”, the court was told.
Mr Harbage said the jury would hear evidence from experts about the way in which smoking cannabis could contribute to paranoia.
He said: “The psychiatrists all agree cannabis, even if it does not directly cause paranoid psychosis, greatly aggravates a pre-existing condition.”
The court heard psychiatrist Gwillam Hayes, who examined Middlebrook after the killing, concluded his illness could be termed “drug-induced”.
Mr Harbage added: “We say he has to face up to the situation he has brought on himself. He has to take full responsibility for his own actions.
"He had an abnormality of mind, but it was self-inflicted - in that it was caused or contributed to by his stubborn taking of cannabis.”
Miss Barton – known as Stevie – was found dead at Middlebrook’s home in Larkspur Croft, Boston, Lincs, early on the morning of December 4 last year.
Police forced their way into the property after being alerted by Middlebrook’s mother in response to a text-message she received from him.
Middlebrook told her: “I’m sorry for everything. Hopefully you’ll be better off without me. I love you. I love her, but it had gone too far.”
Arriving to discover Middlebrook had barricaded himself in a bedroom, officers broke in and found Miss Barton lying dead on the bed.
Middlebrook, who was naked and had self-inflicted wounds to his neck and wrists after trying to kill himself, was detained after a struggle.
Officers and paramedics noticed the “pungent smell” of cannabis in the room and found roach ends on the floor, as well as empty cans of beer.
Three days later, when he was finally fit to be interviewed, Middlebrook claimed he stabbed Miss Barton because he feared for his own life.
He suggested she was involved in a plot to murder him, insisting: “She was in cahoots with a group of lads who are trying to kill me.”
Mr Harbage said: “He said their relationship had been far from good in the days leading up to the killing. He felt torn apart by his mistrust of her.”
The jury heard Middlebrook attempted sex with Miss Barton before attacking her with a kitchen knife, a craft knife and a machete-style cauliflower knife.
He stabbed her three times, tried to knock her out with such force that he broke her jaw and then repeatedly knifed her again in the chest and neck.
Tests later showed Miss Barton, whose aorta, jugular vein and heart were all penetrated in the frenzied attack, had also been smoking cannabis.
The defence claim Middlebrook, who denies murder but admits manslaughter on the grounds of diminished responsibility, was schizophrenic.
But Mr Harbage said the killer made his mental problems worse by continuing to smoke cannabis “despite consistent advice to the contrary”.
Giving evidence, Middlebrook’s mother Denise said she was shocked to learn of her son’s drug use after he attempted an overdose in August 2006.
The former teacher said: “It made sense of some of his mood swings. I don’t think he was a regular user - I think they call it a recreational user.
“He told me some time ago he had tried drugs at college, but he wouldn’t tell me which ones. I thought he had more sense than to use them.”
Asked to describe her son’s character before he started taking drugs. she said: “Honest, trustworthy and reliable - and very even-tempered”.
But she said Middlebrook became convinced people were “after him”, adding: “Marc was just terrified somebody was coming for him with a chainsaw.
“He wasn’t sure whether Stevie was a ’plant’, because some of the answers she gave to the questions he was asking her were inconsistent.”
The trial continues.
By ANDREW PARKER Published: 06 Oct 2008