A sheriff expressed frustration after being asked to deal with a notorious murderess serving life, for throwing punches in prison.

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

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

Two and a half years ago she was given an additional 18 month sentence, 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 a woman she had a grudge against.

On Friday she pleaded guilty by solicitor's letter at Stirling Sheriff Court to assaulting another inmate at Cornton Vale Prison, near Stirling, where she is serving her sentence.

Earley, who was not personally present, assaulted fellow lag Melissa Sloan by repeatedly punching her on the head in the incident in the all-female jail.

Miss Sloan, 32, of Paisley, Renfrewshire, is understood to have been released since the battering that she received at Earley's hands, which occurred on November 14 last year.

Prosecutor Ruariadh Ferguson said he could not provide the court with Earley's expected date of release, or say when she might next be eligible to apply for parole.

Sheriff William Gilchrist deferred sentence until March 16 for Earley to be brought to court.

He also called for a report from the jail's governor.

The case is on summary complaint - less serious than "solemn", or indictment, procedure - meaning any sentence can only be measured in a maximum of a few months.

But he said: "I'm not sure what the court's supposed to do with someone who's serving a life sentence for murder, for punching another prison.

"What am I supposed to add to that?

"I don't see what I can add to it, or what I could do that couldn't be done by the prison governor."

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 that 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.

High Court judge Lady Dorrian told the then teen: "The injuries you inflicted were the result of repeated kicking and stamping to the face and body with a series of blows targeted to the face and neck.

"Mrs Gray had defensive injuries to her hands indicating that she tried to protect herself from your attack.

"The social enquiry report records that your guidance teacher indicated that violence is a part of your make up. You certainly have a previous conviction for assault, and the whole picture here is one of significant violence."

The victim's family said the sentence was "a joke" and Earley should have had a minimum term of 30 years.

Earley became one of Scotland's youngest-ever murderesses when she committed the crime.