A 17-year-old girl who murdered a teenage boy at a party has been detained for life and will serve at least 16 years in custody.

The youngster, who was pregnant and high on cocaine and alcohol at the time of the attack, stabbed 18-year-old Conner Cowper in the neck in a flat in Holytown, North Lanarkshire, in April 2017.

The trial heard claims that the victim had “fancied” the girl but she kissed another man that evening.

The girl became angry when Conner branded her a “stupid wee girl”, grabbed a knife and stabbed him before running away.

The victim was left with a 4in (11cm) deep wound.

The court heard how she left him to die and officers found her nearby “laughing”.

The trial heard how she later asked an officer: “Can I have my knife back? It is good for cutting onions.”

She was convicted at Glasgow High Court last month but her sentence was delayed while reports about her character were obtained.

At the High Court in Edinburgh, judge Lord Arthurson ordered the girl, who cannot be named for legal reasons, to serve at least 16 years in custody.

He told her: “Your attack upon him was deliberate, brutal, unprovoked and entirely murderous, and this murder was committed by you at the age of 17 when you were still a child, while you were under the influence of cocaine and alcohol.”

He continued: “I have been told that not only do you feel regret but you also expressed empathy towards the victim.

“However, as the presiding judge at your trial I saw nothing of that. Your demeanour was flat and disinterested and you didn’t give out any significant appearance of empathy.

“You are a highly dangerous and unstable individual. The attack on Connor was deliberate, brutal, entirely unprovoked and entirely murderous.”

He added: “It was a deliberate, brutal and entirely murderous attack.”

The girl denied murder and claimed she stabbed Conner because she thought he would hit her and that she was affected by a previous abusive relationship.

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The girl is thought to be one of Scotland’s youngest female murderers and is now a mother, having given birth while on remand.

She was expelled from school aged 11.