Nine of the 10 teenagers found guilty of murdering Jack Woodley are set to appeal their convictions.
The 18-year-old was stabbed in the back with a "Rambo-style" knife after a group of youths surrounded and attacked him in Houghton-le-Spring last October.
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".
One 15-year-old admitted delivering the fatal knife blow, but the jury found all 10 guilty of murder.
Ahead of their sentencing, expected to take place on Friday 4 August, nine of them have 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."
The case is thought to have been one of the first times as many as 10 defendants have been found guilty of one murder.
JENGbA (Joint Enterprise Not Guilty by Association), a group which campaigns on behalf of those convicted under the controversial Joint Enterprise law, is supporting families of the defendants.
Jan Cunliffe, one of the founding members of the group, said she had not come across another case with so many defendants being convicted of murder.
"This case is quite unique, to have all 10 convicted of murder when there was only one carrying a knife," she said.
"To the best of my knowledge that hasn't happened. And they are all such a young age."
The court heard how Jack had enjoyed a day out at the Houghton Feast funfair with his girlfriend when he was attacked by the strangers.
Mobile phone footage played in court showed the teenagers approach and surround Jack and one can be heard to shout "get the chopper out".
The group punched, kicked and stamped on Jack during the attack.
Judge Rodney Jameson warned the minimum terms of all their life sentences would vary. He said: "I anticipate there will be substantial variations in the minimum terms."
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