Parents won't forgive

The family of a young New Zealand man kicked to death by three Sydney teenagers say they will never forgive his attackers and hope they receive lengthy jail terms.

Christopher Leicester's mother wept as she read her victim impact statement in the NSW Supreme Court on Friday.

One of the offenders also cried when he entered the witness box and vowed never to drink again and never to re-offend.

Christopher was walking to a party in Sydney's south, when the boys mistook him for someone who had verbally abused them.

He was king hit, fell to the ground and then repeatedly kicked about the head. He died hours later in hospital.

June James told the court she caught the first available flight from New Zealand to find her son on life support. "I could read the monitors and watched his vital signs until his heart stopped."

Two of the boys pleaded guilty to manslaughter and the third pleaded not guilty, but was convicted of the same offence at trial.

All three boys have been in custody since the attack.

Justice Peter Hall will deliver his sentence on October 30.

He challenged arguments that their "immaturity" and alcohol should be considered as factors in the case.