A woman killed her partner and their four-year-old daughter to prevent the world being taken over by vampires, a court has heard.

Shelley Christopher, 36, was mentally ill when she stabbed 42-year-old Richard Brown 29 times and her daughter Sophia six times before inserting wooden objects into their bodies.

Christopher also attacked another child and put a pencil in her body, but despite her injuries, the girl survived, prosecutor Crispin Aylett QC told jurors. She cannot be identified.

Christopher, of Notting Hill in west London, went to a mental health unit in north Kensington in February, two days before the killings, and told staff that someone was out to get her. She refused pleas to stay at the unit and went home.

She is on trial at the Old Bailey on two counts of murder and one of attempted murder, which she denies by reason of insanity.

Opening the trial, Aylett told jurors: “I’m afraid that this is a distressing case which you will find both terrible and tragic. Ms Christopher was later to tell a psychiatrist that, on the day of the killings, she had received a signal instructing her to kill her family in order to prevent the world from being taken over by vampires.

“The signal had come from a lightbulb in the ceiling. She had done – or tried to do – what she was told. After she had attacked each of them with a knife, the lightbulb had told her to put something wooden into each of their chests in order to stop them from becoming vampires.

“That Ms Christopher must have been mentally unwell at this time is borne out by the findings of the doctors who examined the victims. From Richard’s chest cavity, the pathologist recovered part of a child’s paint brush. The pathologist who examined Sophia’s body retrieved part of a pencil.”

A psychiatrist concluded that Christopher, who is now in a secure hospital, had been suffering from a psychotic illness, most likely paranoid schizophrenia, at the time.

Aylett told jurors that when a defendant enters a plea of not guilty by reason of insanity, it was for them, not a judge or psychiatrist, to decide the case on the evidence.

Police found the bodies of Brown and Sophia when they went to the family home on 27 February, days after the killings.

They discovered Brown in the bath and Sophia in bed with a towel over her face, the court heard. Her chest had been covered with coloured plasters and a plastic flower was placed in her right hand.

Social services alerted officers after Christopher attended St Mary’s hospital with the injured child the day before. When doctors operated, they removed a 6.5cm-long broken pencil from the child’s chest.

After her arrest, Christopher told a psychiatrist the colours red, orange and green had become significant to her, with red meaning that she or someone in her family was going to be killed.

She said she had left the mental health unit at St Charles hospital before her assessment was complete because she thought there were vampires there.

On 19 February, she said she had received an orange signal instructing her to kill in order to prevent the world being taken over by vampires. First, she attacked the surviving child, by strangling and then stabbing her with a plastic flower and a small knife.

When Brown arrived with Sophia and asked what was going on, Christopher said: “You’re one of them. You’re a vampire.” She then stabbed him repeatedly in the chest.

She told the psychiatrist that Brown’s eyes had changed colour and he had tried to bite her with his fangs. According to her account, Sophia cried out “no mummy!” and when Christopher asked her if she was “one of them”, the girl replied “yes, I am mummy,” so she stabbed her too.

Aylett told jurors that if they agreed with the assessment, Christopher would receive a hospital order and return to the secure unit where she would remain “for some considerable time to come”.

The case continues.

