A SINGLE mum whose one-year prison sentence for robbery was halved after a judge showed mercy following the breast cancer death of her sister, has fought off a bid by the nation's top law officer to keep her behind bars for longer.

Leanne Knox, aka Leanne Stewart, aged 28, of Duncombe Road, Bolton, was jailed for 12 months in January after pleading guilty to the robbery of acquaintance, Lillian Edwards.

But, after hearing of her 34-year-old sister's recent death, Judge Anthony Rumbelow recalled her to court a week later and cut the sentence to six months.

On Monday, Sarah Whitehouse, representing the Attorney General, Lord Goldsmith QC, argued the judge had been wrong to make so great an allowance and had imposed too lenient a sentence in the first place.

But the nation's top judge - the Lord Chief Justice, Lord Phillips - Lord Justice Latham and Mr Justice Treacy, sitting together at London's Criminal Appeal Court, disagreed and upheld the six-month term.

The court heard how Knox, a mother-of-two who has a string of previous convictions targeted Miss Edwards as she walked along a street in Great Lever on April 23, 2006.

After she refused to give the pair cigarettes, she was pinned to the ground and robbed of her mobile phone, cigarettes and a silver mirror. As she walked away following the attack, Knox threatened to attack her if she reported the incident to the police.

Miss Edwards was so scared of the threat, which she believed to be genuine, that she did not report the incident until June.

Knox was arrested and denied the offence, but was later identified by her victim and changed her story.

Upholding the six-month sentence, Lord Justice Latham said: "Acknowledging as we do that this was an offender with substantial previous convictions, nonetheless there was room for this judge to conclude that he could give proper effect to the plea of guilty and the particular mitigation relating to the death of the offender's sister. In doing so, he was exercising the right of all judges to extend mercy.

"This sentence, in our judgment, was lenient, but is not the sort of sentence with which this court should interfere."