A coroner's report has highlighted problems with the care of a teenager who murdered her former boyfriend's mother.
But the coroner says the tragic outcome could not have been foreseen.
Tonia Bennett was 16 when she set fire to Lynette Chapman's house in Pukekohe in 2009, trapping Ms Chapman upstairs.
Bennett was living in a house in the same street, supervised by workers contracted to Child, Youth and Family.
She was sentenced in 2010 to a minimum of 11-and-a-half years in prison.
In her findings, coroner Morag McDowell says that a supervisor at Bennett's house should have asked her basic questions about her plans for that night.
However, Ms McDowell says that still may not have prevented the murder, and the supervisor could never have predicted what Bennett was doing.