Ten teenagers have been sentenced to a total of 124 and-a-half years for murdering an 18-year-old as he walked home from a funfair.
Jack Woodley was stabbed in the back following an evening out at the fair in Houghton-le-Spring in October last year.
He died in hospital the following night.
Ten males, aged 14 to 18, were convicted in June after a trial at Newcastle Crown Court in which witnesses described how Jack was "isolated" by a mob who were "like zombies attacking an animal".
The 15-year-old who admitted to inflicting the fatal stab wound was sentenced to life with a minimum term of 17 years. He pleaded guilty to manslaughter before the trial began, but a jury found him guilty of murder.
Judge Rodney Jameson told him: "The fact you had a knife was not a secret. You knew Jack was unarmed.
"Instead, knowing he was unarmed and not looking for trouble, you decided to use violence.
"You stabbed in once to the right hip. You had the opportunity to withdraw. Instead you picked your moment to attack again and you stabbed him fatally in the back.
"You are being given a sentence longer than you have been alive. You will be 32 by the time you are eligible for release."
The youngest defendant, who is 14, was sentenced to a minimum term of eight years.
Judge Jameson said he was described by as a psychologist as a "vulnerable young boy".
The judge said he effectively had a learning disability and it reduced his capability.
He told him: "What you did was bad. You're not as much to blame as most of the others in the dock. You may find custody more difficult to deal with."
He is going to be eligible for release when he is 22-years-old.
The other eight defendants were sentenced to between eight and 15 years’ detention.
During the trial, mobile phone footage was played which showed the teenagers approaching and surrounding Jack. One can be heard shouting "get the chopper out".
The group punched, kicked and stamped on Jack during the attack. Witnesses described it as like "animals attacking prey."
Ahead of sentencing, nine of the defendants launched a bid to get their convictions overturned.
A spokesman for the Crown Prosecution Service (CPS) said: "We can confirm that we have now received notices to appeal against conviction from nine of the 10 defendants found guilty in this case."
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