Judge Cameron said the man suffered serious injuries. He was unconscious and unresponsive in the critical care unit with swelling to the brain for four days before he was transferred to the surgical ward for seven days.
In the victim impact report, Judge Cameron told the court the man had no memory of the attack and could not concentrate for a long time afterward. His family and friends reported that he was unable to speak coherently. He still tired easily and prior to August he could not drive. The man still felt unsafe walking about the streets at night.
Judge Cameron said the attack had a significant and lasting effect on the victim's mother and father.
Guilford's lawyer Debbie Goodlet was critical of the court report, which she said was "unhelpful", and that as a 17-year old he had never had the opportunity for rehabilitation. Judge Cameron said he had previously been offered anger management.
O'Neill's lawyer Richard Leith said his client had been on curfew without electronic monitoring since January 16 and that he deserved some credit for the restrictive bail period.
Mr Leith said his client was young, naive and immature at the time of offending, and submitted that the starting point for sentencing should be reduced to five years from eight years. However, it was O'Neill who threw the first punch, Judge Cameron said.
Crown prosecutor Lance Rowe said that by law, both O'Neill and Guilford had received discounts for their age. Guilford was 16 at the time of the crime and O'Neill, 18.
On a charge of possession of an offensive weapon, O'Neill and Guilford were convicted and discharged.
O'Neill was also warned by Judge Cameron that he was subject to the three strikes law.