A teenager stabbed a 15-year-old boy in the neck during a cocaine, ecstasy and alcohol-fuelled house party.
Leroy Allen, 19, attacked the victim from behind, inflicting a "deep cut" and permanent scar, stretching across the back of his neck.
Yet when the victim collapsed in pain, Allen's friend Charlie Agnew, 18, kicked the defenceless boy in the head.
Liverpool Crown Court heard there were up to 30 teens at the home, in Rock Ferry, Wirral, early on March 18, 2017.
Henry Riding, prosecuting, said it appeared they had all been drinking and taking drugs, including the young victim.
Doctors found the boy may have had as much as 179mg of alcohol per 100ml of blood – over twice the drink drive limit.
Mr Riding said: "He, in addition to whatever drugs he admitted, may also have been taking cocaine and ecstasy on the night in question.
"The victim also describes both defendants and indeed a third individual as being 'off their heads on cocaine'."
Mr Riding said the boy fell out with the third person, who may also have been underage, leading to a kitchen fight.
The victim said this third individual was a friend, but used to bully him, and while it was initially "horseplay", he fought back.
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The court heard the boy was getting the better of the third person, but Agnew started punching and kicking the victim.
The boy told police he wouldn't have complained about this fight, but as he retreated backwards, he felt a blow to his neck.
The victim turned around to see Allen, who ran outside, then went after him, but collapsed and realised he was bleeding.
Mr Riding said: "Agnew then followed them outside and kicked the complainant in the face while he was upon the ground."
He said the victim claimed the kick caused a black eye, but there were not any photos of this injury, and it couldn't be said when it was caused.
The victim was taken to Alder Hey Children's Hospital, where he was treated for the cut, from the back of his right ear to the left side of his neck, extending down to his muscle.
He underwent surgery to close the wound and remained in hospital for three days.
Allen, who has a past conviction for battery and threatening behaviour in 2014, was arrested that March.
However, after he was bailed, he failed to attend a police station in May, and was at large for nearly two years.
He was caught in a car containing around £40,000 of heroin at Southwaite Services, off the M6 near Carlisle, on February 19, 2019.
Allen admitted possessing heroin with intent to supply in relation to almost half a kilo of the Class A drug.
He was jailed for three years and four months in April 2019 and was not due for release until October this year.
Allen denied wounding with intent, while Agnew denied assault causing actual bodily harm, ahead of a trial.
However, on the opening day, prosecutors accepted guilty pleas to wounding and common assault respectively.
Mr Riding said the victim was in custody serving a sentence himself and refused to leave his cell to attend the trial.
Lee Bonner, defending Allen, now 22, of Paterson Street, Birkenhead, said he was genuinely remorseful.
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He said: "It was a somewhat spontaneous attack from an immature young man – as he is described in the pre-sentence report – unfortunately, as with many others that night, affected by the consumption of alcohol and drugs and reckless as to the harm which he caused.
"The defendant describes in his pre-sentence report that he was utterly shocked by his actions and though he thinks that the complainant has forgiven him, he describes how he has not forgiven himself, and regrets his actions that night more – I quote – 'more than anything in his life'."
Mr Bonner said Allen had a "difficult" life, including losing a friend aged 11 to a traffic accident, which led to mental health issues.
He said he had ADHD and dyspraxia, was thrown out of his home by his mum at 15, left school without qualifications, and began "mixing with the wrong people".
The lawyer said Allen had since reconciled with his family, was drug free, hoped to move out of the area, and was "a different person".
Agnew, now 22, of Parkview Close, Birkenhead, who has a past conviction for threatening behaviour in 2014, was also described as remorseful.
Anna Duke, defending Agnew, said he too was homeless at the time and "to all intents and purposes ostracised from his family and living a nomadic lifestyle".
She said he was now supported by his family, including a brother-in-law who hoped to give him a job, and had "completely turned his life around".
Judge Rachel Smith said Allen used a weapon to cause a "substantial laceration" and "permanent scarring" to the boy's neck.
She jailed him for 27 months, consecutive to his existing sentence.
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The judge said Agnew maintained that when he kicked the boy, he didn't know he had been stabbed, which was not challenged.
However, she said: "A kick to the head of someone on the ground always carries the risk of serious injury."
Judge Smith added: "The assault by you on him at that stage was entirely gratuitous – it was unnecessary.
"You were not acting in your self-defence or in the defence of anyone else, even if you had been doing so earlier in the incident."
She handed him an 18-month community order, with 200 hours of unpaid work, and a 10-day Rehabilitation Activity Requirement.