The judge sentenced the defendant to three years detention in a young offenders' institution.
He will serve half before he is released.
15:10
'You were not the instigator of this violent incident'
The judge said: "You were not the instigator of this violent incident. You did not introduce the knife."
15:07
'I accept the remorse is genuine'
The judge said: "You are still only 17. You have a single conviction recorded against you.
"I accept the remorse is genuine."
15:03
'You issued a number of blows'
"During the course of the scuffle the knife was dropped and you used it against Matthew Dale, causing him a deep stab wound to his back and incisions to his clothing indicative of it being more than one blow.