A 15-year-old girl faces a life sentence for the “cold, calculated and callous” murder of a mother and daughter committed with her teenage boyfriend, with whom she had a toxic “Bonnie and Clyde”-style relationship.

The teenager, who cannot be named, was 14 when she and her boyfriend, also 14 at the time, stabbed Elizabeth Edwards, 49, a dinner lady, and her 13-year-old daughter Katie as they slept at their home in Spalding, Lincolnshire.



Following the killings the teenage couple took a bath to wash off the blood, had sex and watched four Twilight vampire films, abandoning plans to kill themselves, the court had heard.



The girl had denied murder but admitted manslaughter on the grounds of diminished responsibility. The boy, who also cannot be named, admitted murder at the start of the trial. A jury at Nottingham crown court – who heard that the defendants’ toxic relationship had led to the killings – took two-and-a-half hours to convict the girl of murder following a five-day trial.



The jury heard she was the “driving force” and had confessed her role in matter-of-fact police interviews, giving a “hideously and tragically” true account of the attacks, which had been planned four days previously.

Defence psychiatrist Indranil Chakrabarti told jurors the teenager was suffering from an adjustment disorder and had not been acting rationally while plotting and helping to carry out the killings.

But forensic psychiatrist Philip Joseph said it was “blindingly obvious” that the girl was in a state of emotional turmoil rather than mentally ill.

Joseph told the court the killings were fundamentally all about the relationship between the killers. He said: “A group dynamic can lead you to a course of action you would never have contemplated on your own. Bonnie and Clyde … that sort of intense attraction, emotional closeness – them against the world. It’s that sort of thing that led on to this.

“If they hadn’t got together and had the intense, toxic relationship they [the killings] would never have happened.”



Joseph told the court that, when he interviewed the “inappropriately upbeat” girl over two-and-a-half hours in September, she did not look upset or show remorse. He added: “This is clearly a planned, controlled killing – there is control all the way through it.”

The girl told officers she had “felt like murdering for quite a while”. She said the plan was hatched after a conversation that began with a joke that turned serious. She told police: “We went over the plan over and over again.”



In interviews with police and assessments with psychiatrists, she said the killings had been “a breeze”.



The bodies of mother and daughter were found on 15 April when police officers forced their way into the house. The older woman had been stabbed by the boy eight times, twice in the throat to silence her screams and cries for help. One blow injured her jugular and another almost severed her windpipe. Her other injuries suggested she tried to fight off her attacker.

The younger victim was stabbed twice in the neck then smothered by the boy. The kitchen knife used to kill both was found discarded in Katie’s bedroom.



The defence barrister, Andrew Stubbs QC, said the girl had been diagnosed as having an adjustment disorder at the time and pointed to her diary entries, which read: “Help me. Death is the only way. Madness is in me.”

After the verdicts had been delivered, Mr Justice Haddon-Cave said it had been an “exceptional case by any standards” and praised the quiet dignity of family members.

Sentencing for both will take place next month. Both killers face indefinite detention at her majesty’s pleasure, the equivalent of a life term for an adult. As the jury returned its verdict the girl initially remained composed in the dock, then began to dab at the side of her mouth with a tissue and appeared to be stifling tears.



Speaking outside court, DCI Martin Holvey said: “This tragedy was distressing for all families involved, for Katie’s school friends, for Elizabeth’s colleagues, friends and children at the school where she worked, as well as having a shocking impact on the wider community of Spalding.

“Today the court has found a 15-year-old guilty of both murders. A teenage boy has also pleaded guilty.

“What makes this case even more shocking is that these two were 14 years of age when they planned and committed these callous, senseless and unprovoked attacks on Elizabeth and Katie.

“This case has left a number of lives in ruins, not only Elizabeth and Katie’s family, but also the two juveniles who committed these horrendous crimes.”

Spalding residents said the two victims were well liked and adored each other. Julie Blanford, a friend of Elizabeth Edwards, told the BBC: “She was very nice, very caring. If you had got a problem you could always talk to her.” Another said she was “very happy” and in a new relationship.

The Rev Mike Chester, from St Paul’s parish church, described Katie, who was a member of the church drama group, as “just the most wonderful, loving, gentle, fabulous 13-year-old”.