During her time as Chief Coroner she investigated many of New Zealand's most high-profile coronial cases, including leading the coronial response to the Whakaari/White Island eruption and the Christchurch mosque shooting.
By her own admission she never dreamed of working as a coroner when she was young, but throughout her life, her true calling for became evident.
"I think my passion is investigation, so that's why the role of coroner is such a good one for me."
Unlike judges in a criminal court, where defence and prosecution teams try to argue their case, coroners help investigate the deaths.
"We are directing the investigation, then when all the information has come in, that's when we make our decision."
She said one of the most important parts of the role for her is making recommendations so similar deaths don't occur in the future.
"That can be as simple as saying that part of the road needs work done on it because this is the third time there's been a crash and the first time there's been a fatal crash.
Another rewarding part of the job is giving the families of the deceased an answer about a death.
"Coroners bring together the medical part of the person's history, their work history, their relationships and bring it in to one document. So sometimes that gives families some comfort.
"You feel like you're doing some good for society."
Her role is to provide coroners with the support they need to do their jobs, and offer guidance notes on how to prepare an inquest and how they should involve all the parties.
As well as this, she liaises with stakeholders including pathologists and police to make sure they're working together on files.
Despite holding the Chief Coroner position for several years, her most memorable case came before her appointment.
Back when she was a lawyer Marshall was working at an inquest regarding the death of a toddler who passed after getting a fever.
"The family had had a previous child die in very similar circumstances."
She said the child was immediately taken to hospital but deteriorated very quickly and there was nothing they could do.
What the inquiry discovered was that there may have been a genetic metabolic disorder that had caused the deaths.
Because the family had another child, she said an expert on the case told them to take their other child to hospital, and he would write a letter stating they needed urgent testing done on that child.
"It kind of impressed me, the fact that everyone was working together to find the truth, opposed to it being parties arguing against each other. So that's what got me interested in the jurisdiction."
But it's not a job for the faint-hearted. Coroners' work is often surrounded by death and heartbreak.
"It does take a toll, I think it takes a toll for everyone in different ways, so I've always been quite honest in myself and sometimes you read a file and it's just really, really sad."
Marshall said they have to be careful about their mental health and she encourages all coroners, herself included, to get psychological supervision at least once a year.
"I think district court judges are the same, in that we should be seeking out professional supervision and that our mental health is being looked after as well as our physical health.
"It's a difficult job, but very rewarding."
