KEY POINTS:
The man who beat and strangled teenager Liam Ashley in the back of a prison van believed Chubb security guards operating the vehicle would stop the attack before it turned lethal.
George Charlie Baker, 25, was yesterday sentenced in the High Court at Auckland to at least 18 years in prison for the August 24 killing.
Crown prosecutor Simon Moore had urged Justice Rhys Harrison to impose a minimum of 20 to 22 years.
In written submissions to Justice Harrison, Baker said guards sitting in the van ignored his assault on 17-year-old Liam, and "must have been deaf" not to have heard what was going on.
Baker killed Liam as the pair were being transported from the North Shore District Court to Auckland Central Remand Prison.
Baker became angry with Liam and elbowed him in the chin.
When he saw the teenager was having difficulty breathing after being punched, he began strangling him.
Though Baker said he did not mean to kill Liam, "his attack on the victim continued beyond what was initially intended as an assault, to taking his life", the submissions - prepared by Baker's lawyer, Tony Bouchier - said.
Baker also claimed he and Liam had earlier tried to kick their way out of the van, and were ignored by the Chubb security guards driving the vehicle. He said he could hear the guards talking in the front of the van, and could make out radio telephone traffic coming from the cab.
"All the guards had to do was look through the window separating the cab from the cubicle to see what was happening, but they did not."
A Corrections Department report detailed a series of miscom-munications, errors and misunderstandings that culminated in the teenager being placed in the same compartment of the van as Baker.
Baker also blamed Liam's death on authorities who had failed to help him with his psychiatric problems.
Baker had attempted suicide while at Paremoremo Prison in the weeks before he murdered Liam, and was supposed to be being checked every 15 minutes at the time of the killing.
Mr Bouchier said a "monumental systemic failure by the state" had failed the Ashley family and Baker.
But Baker accepted full responsibility for Liam's death, Mr Bouchier said.
Liam's mother, Lorraine Ashley, made an emotional speech at the start of yesterday's hearing.
Speaking from the public gallery, she told Justice Harrison of her family's grief and feelings of guilt for what happened.
Her son's death had left the family "at the bottom of a great black pit".
Liam's parents had decided to charge him after he stole his mother's car, expecting a stint in the justice system would teach him a lesson and hopefully deter him from reoffending.
Mrs Ashley said the death had devastated the family beyond repair.
"I look into my husband's eyes and see the same sadness as in my children's ... we will never be the same family."
She said the guilt they all felt was immense, and she could not repair that for her family.
Her children regretted all the family discussions they had regarding Liam's unruly behaviour.
"As Christmas nears we feel more sadness, if that is possible," she said, fighting to hold her composure.
"Liam, our son, brother, grandson, uncle, nephew and friend, rest in peace."
Justice Harrison acknowledged the family's grief, and told Baker: "If you didn't appreciate it beforehand, you must now know the profound suffering and sense of loss you have inflicted on that family."
Imposing the 18-year minimum term, Justice Harrison told the packed public gallery Baker would not necessarily be released when the term expired.
He sentenced Baker to a total of four years, to be served concurrently, on separate charges of aggravated robbery, threatening to kill and wounding with intent.
Baker showed no emotion during the hearing, and did not react to the sentence.
