A 21-year-old man who was stabbed in the heart died 'courageously trying to protect his partner' a judge said yesterday as he sentenced the woman responsible for his death to seven years' detention in a young offenders' institution.

Katy Bown, 18, of Stanley Terrace, Great Yarmouth, stabbed neighbour Shane Boulton, 21, in the heart after an argument involving him and his partner Claire Matheson during which Bown was pushed in the face by Mr Boulton on June 19 last year.

Bown, who was then 17, claimed she stabbed Mr Boulton by accident in self-defence.

She appeared at Norwich Crown Court to be sentenced yesterday after being found guilty of manslaughter earlier this month.

Sentencing Bown to a determinative term of seven years' detention in a young offenders' institution plus an extended term of a further three years meaning six years under licence, Judge Peter Jacobs said he did 'not accept this was a case of loss of control or diminished responsibility' and described it as a 'revenge attack'.

He said after the fight between Bown and Ms Matheson all she had to do was 'simply go home into your house stay with your child and get on with your life' but instead she 'planned revenge'.

He said: 'It's perfectly clear to me you made arrangements for a young friend to take your child temporarily while you went to your kitchen and acquired a large knife.

'It is abundantly clear from all the evidence that your intention was to use it on Shane Boulton or Claire Matheson.

'It may well be your target was to be Claire Matheson but Mr Boulton put himself between you and her and you thrust the knife with at the very least moderate force straight into his chest, killing him by piercing his heart.

'It may be little consolation to his friends and relatives to learn that in all probability he died quite courageously trying to protect his partner from you at the risk of his own life.'

Bown, who the judge said had shown 'no real remorse', was told that if normal release provisions were applied she would be at least 21 and under licence for a further six years.

John Farmer, prosecuting, said Bown had been convicted of manslaughter with aggravating features being a 'knife in a public place' and the issue of 'dangerousness' of Bown.

Mr Farmer said it was the view of psychiatrists that Bown, who has learning difficulties, did not have the mental range to form the necessary intent and for that reason was dangerous because of the 'unpredictability of her behaviour' and the fact 'she couldn't see the consequences of her actions'.

Jonathan Goodman, mitigating, said Bown did not have 'any intent to cause serious bodily harm' to Mr Boulton and urged leniency from the judge.

He said she realised the loss she had caused to the family of Mr Boulton and the fact it was 'forever' and the fact she caused it and was 'in her own way' sorry.

Mr Boulton's father Ronnie, of Havelock Road, Yarmouth, said afterwards he appreciated the judge's comment's about his son but justice had not been done.

He said: 'His comments were all right. Fair play to the judge but where's the justice? There is none.'

A jury of 10 women and two men had returned a majority verdict of not guilty of murder but guilty of manslaughter, by 10 to two, after more than 16-and-a-half hours of deliberation.

The court heard the argument stemmed from the fact Mr Boulton, a keen motorcyclist, had been riding his trial bike in the roads and alleyways near Stanley Terrace while Bown was trying to get her two-year-old child to sleep.

Bown became embroiled in a full-blown argument with Mr Boulton's partner during which she was pushed in the face by Mr Boulton.

Witnesses described Mr Boulton as looking 'shocked' following the stabbing. He took off his T-shirt, looked at the wound and collapsed in the street. Despite the best efforts of paramedics who took Mr Boulton to the James Paget University Hospital at Gorleston, he died as a result of the single stab wound to the heart.

Bown, who Norwich Crown Court heard has an IQ of just 66 (an average IQ is 100) and a 'limited repertoire of coping skills because of her learning difficulties', claimed she acted in self-defence.

Fearing she might be attacked again Bown, who had only moved to the area six months earlier after spending much of her life in Leicester, said she armed herself with a knife to scare off Mr Boulton who she said she had seen with a knife.

The girlfriend of Shane Boulton has been told by a judge that she was 'directly responsible' for the events which led to his death and would have to live with that for the rest of her life.

Claire Matheson, 32, of Dunsop Drive, Bolton, appeared at Norwich Crown Court yesterday to be sentenced after previously pleading guilty to threatening behaviour and possession of a meat cleaver on June 19 last year.

Sentencing Matheson to a four month prison sentence, suspended for a year with supervision, Judge Peter Jacobs, pictured, said: 'I will spare you custody, but I'm not going to spare you emotionally for what I'm about to say.'

Judge Jacobs said Matheson, who the court heard had previous convictions for criminal damage and assault offences, was to blame for kicking off events that led to Mr Boulton's death when she went to see Bown over the motorbike incident which had already been dealt with by Bown and Mr Boulton.

He said: 'You decide you are going to go round and have it out with her. Why is a total mystery to everyone here. She's behaved properly and Shane Boulton's behaved properly, but you have to go round and have to kick the whole matter off yet again and you succeed and everything that happens from then on you're directly responsible for.'