The family of a murdered grandmother have launched legal proceedings in the High Court against an NHS foundation trust.
Sally Hodkin, 58, was murdered by Nicola Edgington in south-east London in October 2011.
Hours earlier, Edgington had walked out of a mental health unit where she was taken by police after her mental health deteriorated.
The 32-year-old, from Greenwich, was jailed for life and told she would serve at least 37 years in prison after being convicted of murder at the Old Bailey in March.
During the trial, the court heard that Edgington had stabbed her mother to death six years earlier but was released to live in the community. She suffered a sudden relapse in her mental health, two years after being released from a mental health unit, in October 2011.
Police took her to the Queen Elizabeth Hospital in Woolwich after staff at a cab firm became alarmed at her behaviour in the middle of the night.
While waiting to be admitted, she rang 999 five times and warned that she was dangerous and would harm somebody if she was not sectioned.
After a delay, she was taken to the mental health unit at the hospital, Oxleas House, which is run by Oxleas NHS Foundation Trust, but walked out soon afterwards. Hours later she attacked Mrs Hodkin, a law firm accounts clerk, with such force that she almost decapitated her.
Yesterday solicitors representing the family of Mrs Hodkin said they have served High Court proceedings on Oxleas NHS Foundation trust, claiming damages for negligence and breach of human rights.
The family claim it negligently failed to realise that Edgington had a previous conviction for manslaughter and failed to detain and treat her as a danger to the public, solicitor Daniel Rubinstein said.
They claim this directly resulted in the death of Mrs Hodkin, the solicitor added.
A spokesman for Oxleas NHS Foundation Trust said yesterday: “At this stage we don’t feel it is appropriate to provide any further comments than those we have already issued.”