A female prisoner who slashed monster mother Theresa Riggi with a razor was sent back behind bars for two years.

Angela Hamilton (40) claimed to have “sympathy” for child-killer Riggi despite being found guilty of sneaking into her cell at Cornton Vale Prison after breakfast and cutting her face with a razor blade.

She left Riggi lying screaming on her cell floor with her face covered in blood and a clump of her hair missing from her head.

As prison guards rushed to Riggi’s aid, Hamilton was captured on CCTV calmly walking back to her cell.

On Friday (3 October) Stirling Sheriff Court heard that Hamilton claimed to have gone to Riggi’s cell to shout for help.

Sheriff William Gilchrist said: “I saw the recording of her going into the cell. There is no question of her seeking assistance for Miss Riggi.” Hamilton’s lawyer, Murray Aitken, agreed there was no evidence she had tried to get help for Riggi but said sound could not be heard on the prison CCTV footage.

He added: “She has sympathy for Miss Riggi in the position that she found herself in and ultimately what happened to her but she denies responsibility for the attack itself.” Sheriff Gilchrist told Hamilton she had attacked Riggi when she was in a “very vulnerable position” and said he had no option but to jail her.

Hamilton denied the attack but a jury of 10 women and five men at Stirling Sheriff Court took little over an hour to find her guilty by majority following a two-day trial.

The assault occurred on 19 November 2011 while Hamilton was in jail serving a sentence for attempting to pervert the course of justice.

Riggi (50) was in her first year of a 16-year sentence imposed for killing her three young children in Edinburgh in August 2010.

Eight-year-old twins Austin and Luke and their sister Cecilia, five, were each stabbed eight times before Riggi, originally from California, tried to cover up their deaths with a gas explosion while attempting suicide by leaping from the window of the second-floor flat.

The family had moved from Skene, Aberdeenshire, the previous month following the breakup of Riggi’s marriage to the children’s father.

Prior to the stabbings Riggi made a chilling phone call to Mr Riggi, telling him to “say goodbye”.

Following the attack at Cornton Vale, Riggi was moved to Rampton Secure Hospital in Nottinghamshire, where she died from bronchial pneumonia in March this year.

During Hamilton’s trial, prison officer Calum Graham told how he went to Riggi’s cell that morning after hearing screaming, saw the accused leaving the cell and then Riggi lying on the floor inside with blood on her face, still screaming.

His colleague James McCabe said his hands and clothing became “covered in Riggi’s blood” as he tried to help her.

On Friday Sheriff Gilchrist told Hamilton he had to send to her prison given the “gravity” of the offence.

He said: “There are obvious concerns about your use of drugs, your mental health problems and concerns about your record but quite apart from that this is a conviction for assault to severe injury involving the use of a razor.” He added: “The person who was attacked was in a very vulnerable position.” Sheriff Gilchrist then jailed Hamilton for two years and ordered her to be supervised for a year on her release.