By Chris Summers BBC News

A knife amnesty has come into operation across England, Scotland and Wales. Earlier this year a teenager was jailed for life for stabbing to death 15-year-old Charlotte Polius at a birthday party in east London. The case highlights the danger of knife crime.

This case illustrates once again the utter folly of persons - even female teenagers such as you - who nowadays arm themselves with knives and carry them in public Judge Giles Forrester

The national knife amnesty will come too late for the parents of Charlotte Polius, who was stabbed to death at a party in Ilford, east London in April last year.

A jury at the Old Bailey heard how 18-year-old Beatriz Martins-Paes, plunged a four inch (12cm) kitchen knife into Charlotte's chest as she stood on the landing of her friend's house, surrounded by other youngsters.

Home Office pathologist Dr Vesna Djurovic said the blade entered the heart and cut through two major blood vessels, causing huge blood loss.

When asked if the teenager could have been saved by paramedics she said: "No, I don't think she had any chance of survival."

Charlotte's mother Mary Foley sobbed quietly in the public gallery as Dr Djurovic described the fatal injury.

She later told the BBC's Real Story: "I know looking at Beatriz she has situations in her life that need to be dealt with. I'm not blaming her parents or society.

"She has choices and unfortunately her choice that night was to use a knife on Charlotte. I ask myself why didn't she punch her or attack her and jump on her first ? She needs help whether it's counselling or whether it's believing in Jesus. She needs help before she harms herself."

She has choices and unfortunately her choice that night was to use a knife on Charlotte. I ask myself why didn't she punch her or attack her and jump on her first ? Mary Foley Charlotte's mother

Showing remarkable compassion for her daughter's killer, Mrs Foley said: "Society won't transform her, prison won't transform her. The only thing that will really transform Beatrice is a living relationship with Jesus. She needs a help that society really can't give her. But, I don't know.

"She screamed out in court. She's been crying. I had compassion for her I have to admit, when I heard her crying it reminded me so much of an innocent girl. When she screamed out I won't forget it, I won't.

"She's human. She's such a young girl as well. It's so sad."

The trial heard how Martins-Paes, from Brentwood, Essex, "squared up" to Charlotte over a trivial dispute on the dance floor of the party.

She followed the younger girl upstairs and said: "Are you chucking it [trying it on] ? Do you want to get shanked [stabbed] ? I'll shank you."

Seconds later she stabbed Charlotte, who staggered back into the bedroom fatally wounded.

Martins-Paes, who was British-born but of Portuguese/Mozambican origin, ran downstairs with the bloody knife in her handbag.

Chased

Another party guest told the court: "There was a lot of mayhem and I saw a girl called Beatriz coming out and her cousin called her back. She shouted something in Portuguese and then said 'I don't care, I'll shank (stab) her again'."

The jury heard how Martins-Paes fled the house and was chased by partygoers.

A police patrol car stopped her, thinking she was the injured party, and she got in.

She hid two knives under the car's front seats as it drove off.

Later the police realised she was the prime suspect and she was arrested.

In the witness box Martins-Paes wept when she recounted the incident: "I cannot explain it. It was all unreal. I did not believe it happened. It was just, like, shocking."

Asked why she had lied to police she said: "I knew I had done the baddest thing you could do. I was just trying to justify it really".

Sentencing her, Judge Giles Forrester said: "This case illustrates once again the utter folly of persons - even female teenagers such as you - who nowadays arm themselves with knives and carry them in public.

"The carrying of weapons on the streets is a public menace which can have horrific consequences as this case illustrates.

During the trial one witness, who cannot be named for legal reasons, was asked if fights between girls were common.

"It wouldn't be normal but girls do fight. I don't fight with weapons but most people carry knives."

It is that tendency to carry knives which is so worrying to police officers and parents nationwide.

Beatriz had taken the knife she used to kill Charlotte from her aunt's two weeks earlier and had carried it around "like a fashion accessory".

In a statement following the conviction, Linford Polius, Charlotte's father, said: "Our daughter Charlotte was taken away from us over something that seems so trivial. A few cross words at a party and our lives have been completely destroyed.

"Charlotte had everything going for her and for this reason I, as her devoted father, will never ever forget or be able to forgive.

"We have not detected any hint of remorse from our daughter's assailant but we hope she will have plenty of time to reflect on the terrible consequences of her actions and maybe in time she will show some genuine remorse."

Aftab Jafferjee, prosecuting, said the case "exposed a new and sinister development in our urban society - the carrying of knives by teenage girls".

Announcing the knife amnesty - which will run from 24 May to 30 June - Home Secretary Charles Clarke said police forces in England, Scotland and Wales would be trying to persuade people to hand in weapons.

Tackling knife culture, especially among young people, is paramount to the safety of our communities, and I am determined to reduce the devastation caused by knife crime Charles Clarke Home Secretary

He said: "Tackling knife culture, especially among young people, is paramount to the safety of our communities, and I am determined to reduce the devastation caused by knife crime.

"The message of this campaign is simple - carrying knives on the streets will not be tolerated."

Last year there were 12,000 knife-related offences committed in London and in December the Metropolitan Police launched Operation Blunt in an attempt to tackle knife crime in the capital.

'Escalates the violence'

Officers are visiting every secondary school in London in an attempt to educate children aged between 11 and 16 of the dangers of carrying knives. Pupils will be shown a video which underlines the consequences of knife crime.

A Met spokesman said: "If you carry a knife you are more likely to become a victim of crime and more likely to get a criminal record. Bringing out a knife escalates the scale of violence."

He said a fight involving fists was unlikely to end in serious injury whereas if a blade was involved it was all too easy for it to end in death.

Charlotte, from Stratford, east London, left behind her mother, stepfather Paul, 10-year-old brother Dion, and a three-year-old stepsister.

The Real Story interview with Mary Foley will be broadcast on Monday 5 June at 1930 GMT. The programme focuses on the work of police family liaison officers.