teenager who was crazed by high-strength cannabis butchered a grandmother after 'voices in his head' told him to stab a woman.

Ezekiel Maxwell, a paranoid schizophrenic, launched the horrific attack after years of smoking super-strength 'skunk weed'.

The 17-year-old claimed 'gangster voices' from the ultra-violent computer game Grand Theft Auto had set him on a mission to stab a black woman.

He is the second teenage cannabis addict in a month to be found guilty of killing others after smoking the substance. Thomas Palmer, 18, was jailed for life for murdering his two friends with a hunting knife near their homes in Wokingham, Berkshire.

Maxwell prowled the streets with a kitchen knife until he came across Carmelita Tulloch

Maxwell prowled the streets with a kitchen knife until he came across Carmelita Tulloch as she walked to her job at a photocopying firm.

He stabbed her seven times, leaving her to die in a pool of blood as he fled home to his family. The case highlights the dangers of the highly potent 'skunk'.

The number of under-18s treated for smoking the drug has doubled to nearly 10,000 in a year and medical experts said the link between it and mental health problems is now impossible to ignore.

Maxwell attacked 51-year-old Mrs Tulloch on September 5 last year after a night smoking skunk and playing Grand Theft Auto.

He believed he was one of the principal characters called Carl Johnson, who carries a knife in the Playstation game, Croydon Crown Court was told.

Judge Warwick McKinnon said it was "a vile and quite senseless killing of an entirely innocent woman".

Simon Denison, prosecuting, told the court: "Maxwell had been planning to stab a woman for seven days, it had to be a black Afro-Caribbean woman. He didn't know why he had done it, he just had to do it."

"He described the voices as taking over his thoughts and his body. They made him do things like cut his hair so he looked more like a gangster.

"Maxwell said in the months before the killing he was playing Grand Theft Auto to the exclusion of anything else.

"He had smoked cannabis the night before, he took a knife from the kitchen and went out to stab someone. After he stabbed Mrs Tulloch he ran home and told his mother what he had done.

"The psychiatric assessment is that he is a great risk to others and will be for many years."

Maxwell lived 500 yards away from Mrs Tulloch on the same housing estate in Kennington, South London. He attacked her within five minutes walk of her home.

The youngster started smoking cannabis and skunk as well as taking cocaine at 14. He had previously been given cautions for possessing cannabis and has two convictions for mugging and assault.

Maxwell said he started hearing voices after smoking the drug and was referred to a psychiatric team by his GP in June last year.

He was prescribed anti-psychotic drugs and his case was reviewed four times. It was due to be considered again the day after he attacked Mrs Tulloch.

Instead, Maxwell went to a police station with his uncle and solicitor and handed himself in. He told officers: "I am given medication for my head and eyes, I don't know why I have been told to take this medication. I have not taken it for two weeks.

"On September 4 I played Grand Theft Auto until late. When I got up I felt a bit unhappy and aggressive. "I went out of the house at about 10am."

"I have a knife with me. I didn't know why I had a knife, I saw a woman, I stabbed her with the knife, I stabbed her three times, there was a lot of blood. After I stabbed the woman I ran home."

Maxwell has since been diagnosed with schizophrenia. Yesterday he was detained indefinitely under the Mental Health Act after pleading guilty to manslaughter on the grounds of diminished responsibility.

Paul Jenkins, chief executive of mental health charity Rethink, said: 'While there can be several triggers for mental illness, we know that if used by people under 18, cannabis doubles the risk of psychosis.

Professor John Henry, a clinical toxicologist, said: "People are beginning to realise that cannabis is not the puff and relax substance that people used to use."

Studies show there is an increased instance of schizophrenia in cannabis users, in some people as much as a ten-Marjorie Wallace, Chief Executive of mental health charity SANE, said: "This has all the hallmarks of similar stories where a paranoid schizophrenic has not taken medication but has used cannabis.

"Cannabis, especially skunk, can act as a trigger to psychotic relapse in which someone may lose touch with reality and become a serious risk to himself and others.

"We expect the inquiry into this case will reveal the same faultlines underlying many of the 55 homicides involving mental illness each year."

Mrs Tulloch, a receptionist, was married to Prince, 42, and had two adult daughters, Claudia and Andrea, from a previous marriage and a threeyearold granddaughter called Tianna.

Her sister Carol Smith said: "Someone has to take responsibility, how can he commit a crime like that and no one is responsible?

"There need to be regular check-ups for people like him."

Its so easy to blame a video game. It was his fault and the parents. He had enough control over himself that after stabbing that poor lady 7 times he ran home like a pussy. I swear idiots like that should be put to death

Mirrors my thoughts. Does the UK have the death penalty?

Yeah, that's what I think. I think the death penalty should be reserved for those types of cases where there is no disputing whether or not the person did it. It doesn't have to be the solution for EVERY case, but it can be easy enough for a case like you mentioned.

There should not be one man that can be Judge and Executioner.

Our justice system is pretty flawed imo. Should just shoot the guy in the head, easy for me to agree with Supa on that one. We are so inefficient with prisoners on death row, even ones that were on video tape or have multiple witnesses saying they did it. People sit there for years and leech tax dollars when they should be dead. Killing people that were wrongly convicted is bad, but that is extremely rare. Every person who I have met that has been to prison has told me they weren't convicts, but just inmates. They all tell you they were innocent. Most of them aren't, and I am willing to sacrifice a few innocents to expedite the death of hundreds of real killers on death row. There is a reason why countries with stiffer death penalties than ours have much lower murder rates (Singapore hasn't had a murder in several years last I read lol).