Warning: This story deals with suicide and may be upsetting.
The family of Nicky Stevens, who took his own life while in mental health care, will take their battle for an apology and compensation to Prime Minister Jacinda Ardern.
Dave Macpherson and Jane Stevens, together with their other son, Tony Stevens, will meet with the Prime Minister on Wednesday to discuss the case.
Nicholas Taiaroa Macpherson Stevens died after he left the Henry Rongomau Bennett Centre at Waikato Hospital on unescorted leave, against the express direction of his parents.
The 21-year-old musician, who suffered from schizophrenia, disappeared on March 9, 2015, and his body was found three days later in the Waikato River.
It took police two days to mount a search for Nicky, a failing criticised by the Independent Police Conduct Authority.
In December, following a three-day inquest last June, Coroner Dr Wallace Bain ruled Nicky's death was avoidable.
In his report Bain said the treatment Nicky received by Waikato District Health Board was well short of what he and his parents would have expected.
"As a result of the deficiencies in his care, he took his own life in the precise manner and place that he had previously said he would."
But in February the DHB, where Macpherson was a board member until this month when the board was sacked by Health Minister David Clark, launched an attack on the findings.
Through its lawyer, Paul White, the DHB made the unprecedented move of writing to the Solicitor-General to ask for a new coroner on the case, claiming concerns over "procedural errors" and Bain's conduct.
The move, which shocked and angered Nicky's whānau, was slammed by mental health advocate and New Zealander of the Year Mike King as disgraceful.
One of the allegations related to evidence from a witness, Australian consultant psychiatrist Dr Nick O'Connor, who was a member of the team that reviewed the DHB's care of Nicky during the period leading up to his death.
The DHB claimed Bain dismissed the views of O'Connor without giving him an opportunity to be heard at the inquest.
But Stevens and Macpherson said it was "factually completely incorrect to claim that the Coroner 'dismissed' the views of Dr O'Connor".
"His evidence was presented in writing and accepted by all parties, including the Coroner, and your own counsel told the court his appearance was not necessary," the couple told the DHB earlier this year.
A transcript of the inquest shows White suggested O'Connor not appear, via video link from Sydney, because it would "delay matters" and "inconvenience everybody".
Bain agreed and accepted the evidence in writing, which he dedicated seven paragraphs to in his report.
Stevens said the request for a new coronial inquest had been a "nightmare" that kept them from getting the closure they sought.
The meeting with Ardern was "now our best hope to bring some sense into this situation".
"We were totally devastated when the DHB challenged the Coroner's findings.
"We waited nearly four years for our son's inquest to happen. Now the DHB has challenged the findings purely because they will not accept accountability for our son's death."
Stevens said their case was one of many families around the country left without any support to face dealing with the legal and bureaucratic processes relating to a suicide, while grieving.
"It's the worst nightmare you can imagine and it just keeps going on."
Macpherson said it would "take some independent and wise heads to assess ways of achieving closure and reparation".
The family will also meet with new Waikato DHB Commissioner Karen Poutasi next Thursday to discuss the situation, which is still being investigated by Crown Law.
Macpherson said he hoped the "politics of kindness and common sense would win out", allowing the family to move on with their lives.