Schoolgirl was apparently murdered for the most mundane reason: she didn’t want to be with her boyfriend any more

• Teenager jailed for life for murdering Holly Newton

Logan MacPhail, then 16, was “calm and emotionless” when he was arrested after repeatedly stabbing his 15-year-old ex-girlfriend Holly Newton. When he was later told he was being charged with murder, he replied simply: “Is she dead?”

Darren Davies, the detective in charge of the murder investigation, remembered that MacPhail’s chilling demeanour was the same throughout police interviews. “For someone of his age to have that lack of emotion did seem weird.”