A teenager has been sentenced to at least 16 years for murdering Harry Pitman on New Year's Eve in 2023.
Harry, 16, was stabbed in the neck in Primrose Hill park, north London, as he and friends gathered to watch fireworks.
Areece Lloyd-Hall, now 18, was found guilty at the Old Bailey last month.
The court heard Harry and Lloyd-Hall did not know each other and were with separate groups of friends.
The trial was told the situation escalated after Harry accidentally bumped into someone from the other group while playfighting.
Lloyd-Hall lunged at Harry with a pointed dagger, metres from where police were stationed.
Footage showed Harry holding his neck, his T-shirt covered in blood, as he pushed through crowds calling for "help".
He collapsed and died minutes later, shortly before midnight.
Lloyd-Hall pleaded not guilty and said he hadn't intended to kill Harry - but was convicted by an 11-1 majority.
It was his second trial after a previous jury was unable to agree on the murder charge.
The judge said the killer's ADHD and PTSD conditions provided some mitigation, but that he bore significant responsibility as he chose to carry and use the knife.
"You stabbed Harry because you lost your temper with him and you acted like a big man in front of your friends," said Mr Justice Cavanagh.
He told Lloyd-Hall: "In the moment, you did not care if he lived or died."
The 18-year-old will be detained in a young offenders' institution until he is 21, when he will go to an adult prison.
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