When he was a young coroner in Christchurch he dealt with a spate of cot deaths, now known as sudden unexplained death of an infant, and he said those were some of the hardest cases he's seen.
"It made one very conscious of how fragile a baby's life is, that kind of helpless feeling you have when you realise that sometimes you just can't control what's happening," he said.
He expressed regret that recommendations coroners had made about cot death weren't responded to.
"There was a consistent message coming through from coroners over the years emphasising the danger of co-sleeping, particularly the danger of co-sleeping when the adult was under the influence of drugs or alcohol or simply sheer exhaustion."
He said it was only after a joint investigation with a university professor that the message began to get out that in some cases there was an explanation for the death and it was an adult smothering the baby.
"If that message had been heeded across the board earlier there would've been a lot of babies that did not die."
He said he wanted to see coroners' recommendations on quad-bikes and their use responded to, and said people will keep dying on the farm equipment if changes aren't made.
Suicide had been a topic the judge had spoken about throughout his career. He said he had seen the attitude towards suicide change from "taboo" to a topic the public and media were "intensely interested about".
"Simply because we have this staggering phenomenon of suicide ... bigger than the road toll now."
Judge MacLean said he was "none the wiser" as to why New Zealand's suicide rate was so high, and said there was no simple answer to any suicide.
The only time in his career he has been kept awake at night by a case was during his management of the body identification process for the victims of the Christchurch earthquake.
"You were living in this artificial bubble of calmness out there in Burnham [Military Camp] while they got on with their task, conscious of the ... devastation just down the road."
His wife and son were at his farewell address, and his wife laughed when Judge MacLean was asked if his new role would mean a slower pace.
Deborah Marshall is the new Chief Coroner.NZME.