A notorious murderer serving life in prison was sentenced to a further six months behind bars for punching another inmate.

Nicolle Earley was jailed as a teenager for killing a grandmother during a row over £5 and a borrowed cigarette.

Earley, now 24, was just 16 when she stamped 63-year-old Ann Gray to death at her home in Crosshill, Fife, in 2008.

She was given an additional 18-month sentence two and a half years ago, to run consecutive to her current sentence, after she sent letters covered in blood and scrawled with swastikas, threatening to torture and kill a solicitor and another woman.

On Wednesday, she appeared for sentence at Stirling Sheriff Court after pleading guilty by letter at an earlier hearing to assaulting a fellow prisoner at Cornton Vale Prison, near Stirlling, where she is serving her sentence.

She assaulted Melissa Sloan by repeatedly punching her on the head.

Ms Sloan, 32, of Paisley, Renfrewshire, is understood to have been released since the attack, which happened on November 14 last year.

The court heard  warders went to Ms Sloan's cell after hearing a commotion and found Earley punching her. Ms Sloan did not require medical treatment.

Sheriff William Gilchrist sentenced Earley to six months in jail to run consecutive to her life sentence.

He said: "You have already received one consecutive sentence for committing offences while in prison. All you are doing is delaying the date when you can be considered for parole.

"Bad behaviour in prison, particularly assaults, will only lengthen that period."

Earley, of Methil, Fife, was jailed for life in 2010 with a minimum term of 14 years for the murder of Mrs Gray, her grandmother's neighbour. Earley was a regular visitor to Mrs Gray's house.

Her trial, at Edinburgh High Court, was told the day before the murder, Mrs Gray had apparently borrowed a cigarette from Earley on the understanding she would give the teenager two in return.

The following evening Earley went to collect them, along with £5 she claimed she was owed for shopping.

An argument followed, in which Earley knocked the pensioner to the ground before repeatedly kicking her and stamping on her.

Pathologists found Mrs Gray died of head injuries.