A coroner says the death of an 87-year-old and his wife was preventable and police missed an important opportunity to stop it from happening.
Ewen Donaldson drove the wrong way up Auckland's northwestern motorway in 2010 and caused a seven-car crash which killed him, his wife Dulce Donaldson and injured three others.
Coroner Katharine Greig has released her findings, saying the deaths were preventable.
Ms Greig said on Tuesday that police missed an important opportunity when they failed to act on a letter from a senior mental health worker saying that Mr Donaldson posed an imminent risk due to a mental health condition.
The letter asked for police to take all possible steps to prevent him from driving, including impounding his car.
Police told the coroner they had no record of having received the letter, but that an off-duty officer may have spoken to Mr Donaldson about his driving.
In a statement on Tuesday, police described the case as an isolated incident.
Katharine Greig wants police to consider whether they need increased powers to impound cars to stop mentally impaired drivers from causing fatal crashes.