You probably shuddered when you read about the terrible thing which happened to a young trainee doctor, Grace Spence Green. Her body was smashed when a man jumped off a 120ft-high shopping centre and landed on her. But did you wonder why it even happened? Marijuana was why it happened.

When will we ever learn just how much damage the unrestrained use of marijuana is doing to our society? When will we ever do anything about it, as wiser countries do?

I make no apologies for coming back to this subject, as I remain amazed by the growing support of ignorant politicians and media for the legalisation of this terrifying poison. If they get their way it will take us straight into a nightmare version of the third world, with all the misery but without all the sunshine.

You yourselves may have seen the symptoms, and you will have been appalled by them – but you may not have connected them with their actual cause, because so many media outlets do not report the vital details.

Grace Spence Green (pictured) was left paralysed by a maniac who leapt onto shoppers from the top floor of Westfield mall

Ms Green was struck on October 17 last year, suffering 'catastrophic' injuries

There are many striking things about the case of Ms Green. There is her courageous, selfless response. This young woman is now confined to a wheelchair, possibly for life. But she is quite without bitterness. She takes comfort because, though she was gravely hurt, she managed to save a life, by breaking the man's fall. She has returned to university to continue her medical studies.

This is very moving. But it also makes me very angry, because all this pain and loss could easily have been avoided by simple, cheap human actions.

The man who jumped, Amsumana Sillah Trawally, eventually admitted grievous bodily harm and was sent to prison, far too late to do him or us or Ms Green any good. The judge said he had, in effect, used his body as a weapon and must have known the risk he was taking. Which is true.

Trawally, 25, was out of his mind on marijuana at the time. He tested positive for the drug, afterwards. But you will say, surely marijuana does not cause people to leap off high places, and land on innocents below, or it would happen all the time.

And I would agree with you. The temporary high given by the drug probably would not normally have that effect. But many terrible acts of violence or insanity or both are committed by long-term marijuana users, who have become mentally ill.

The judge, like so many people in positions of authority in modern Britain, appears not to know of the link between marijuana and long-term mental illness. That judge ignored evidence that Trawally was mentally ill as well as intoxicated, seeing it as nothing more than an attempt to excuse the crime. He said: 'I am entirely satisfied that the offending was attributable to voluntary consumption of cannabis rather than any underlying mental disorder.'

Far from legalising marijuana, we should be ferociously enforcing the laws against its possession, and driving it out of use, as the sensible governments of Japan and South Korea still do (stock image)

In my view the judge was wrong. This issue is nothing to do with responsibility. Possessing marijuana is a crime, and those who inhale or eat it are totally responsible for the other crimes they commit as a result. I'm utterly uninterested in getting them off.

But if only the authorities would look into the past drug abuse of all violent criminals, I think we would find an undeniable link between marijuana use and violence.

If this were done, the Government and the police might grasp that 50 years of slack, weak, sloppy attitudes towards marijuana, and the popular wisdom that it is a soft drug, have been a disastrous mistake.

Far from legalising marijuana, we should be ferociously enforcing the laws against its possession, and driving it out of use, as the sensible governments of Japan and South Korea still do.

But see what a stone wall I am up against here. Half a year ago, I tried to discover from Hampshire Police if they had checked on the past drug use of a very nasty killer.

The culprit was then 17 so his name has not been disclosed. He broke into the home of Barry Hounsome, an academic in Gosport, near Portsmouth, and cruelly killed him for no known reason, using, among other things, an electric drill. He was clearly out of his mind.

I asked if they had looked into his past drug abuse.

But rather than answer my simple question, Hampshire Police acted as if they were guarding the national nuclear codes.

After months of wrangling, and the laudable determination of the Information Commissioner, they last week coughed up a form authorising a drug test on the culprit after he was caught. That's it. That's what they did. No sign of any inquiry into his past. Two parts of nothing. They have had every opportunity to tell me if they ever did anything else. I think I can now fairly say that they did not. They weren't interested. They didn't think it mattered.

Well, thanks to that lack of interest in every police force in this country, more dreadful crimes have taken place, are taking place and will take place, such as the one which burst so terribly into the kind and generous life of Grace Spence Green. This will go on until we wake up. When will that be?

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