A teenage couple detained for life for the brutal killings of a mother and her daughter are to challenge their sentences.
The boy and girl, both aged 14 at the time of the murders, had sex, shared a bath and watched vampire-themed films after the murders of dinner lady Elizabeth Edwards, 49, and 13-year-old Katie Edwards.
Now both 15, the couple were handed minimum terms of 20 years last November by Mr Justice Haddon-Cave, who said the pair had a "toxic" relationship and had acted in a grotesque way after the stabbings in Spalding, Lincolnshire.
Sentencing the pair, believed to be Britain's youngest double killers, at Nottingham Crown Court, the judge said the case had "few parallels in modern criminal history".
He told the teenagers who cannot be named for legal reasons: "The killings were brutal in the form of executions and both victims, particularly Elizabeth Edwards, must have suffered terribly in the last minutes of their lives."
The court was told the boy, who admitted murder, used a kitchen knife to stab both victims in the neck after attacking them as they slept at their home last April.
His girlfriend, who helped to plan the "cold, calculated and callous" killings, denied murder, claiming to be suffering an abnormality of mental function which impaired her ability to form rational judgments, but was found guilty after a five-day trial.
Addressing the couple, who had been likened to Bonnie and Clyde, the judge said: "There was remarkable premeditation and planning, it was, on any view, substantial, meticulous and repeated."
The hearing is due to take place at the Court of Appeal on Thursday.