He was admitted voluntarily to the crisis mental health team in early 2015 and kept in the acute inpatient unit under the Mental Health Act as a patient for three months.
Ex-academic and advocate for Fischer's mother Robert Miller has applied for Coroner Peter Ryan to step down from the inquest, saying the scope is too narrow.
"I think he's biased and I think he's no longer independent," Miller said.
But the coroner has rejected the claims, saying he is satisfied he has not shown any signs of bias.
Miller believed the inquest needed to address wider systemic issues with the treatment of mental health patients, but this was not happening in Fischer's case.
"I've been of the view since shortly after Sam died . . . there had to be some accountability from top management in two DHBs."
Miller believed Coroner Ryan had wrongly ruled certain evidence was irrelevant to proceedings, and felt agencies were working together to protect the DHBs involved.
One "major aspect" was what Miller called "covert planning" to move Fischer to a mental health unit in Porirua, despite suggestions he had threatened to kill himself if that were to happen. Fischer and his family's consent to being moved to the unit is in dispute.
Miller knew Fischer for about two years before his death.
"Sam phoned me and asked can we talk some things through, and that was something that I couldn't turn my back on," Miller said.
During his time as an academic, his specialty was theory of brain function. He is also a previous mental health service user.
Coroner Ryan has declined Miller's application. In his response, he said the application "fails on the first hurdle", as Miller does not have standing in the proceedings to apply for the recusal.
He also said Miller failed to show "the necessary connection between his perceived issues and his apprehension that I might decide the case other than on its merits.
"I am satisfied that I have not demonstrated bias in any decisions I have made to date, nor in the conduct of the inquest."
The scope of the inquiry had been narrowed to look at the circumstances around Fischer's death, in his last admission to the unit.
"It cannot be broadened to become akin to a commission of inquiry into the treatment of patients with mental health issues."
People in top DHB management were excluded from the witness list because they were not involved in Fischer's treatment, he said.
If you are worried about your or someone else's mental health, the best place to get help is your GP or local mental health provider. However, if you or someone else is in danger or endangering others, call police immediately on 111.
Or if you need to talk to someone else:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youthline: 0800 376 633
• Need to talk? Free call or text 1737 (available 24/7)
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Samaritans 0800 726 666
• Rural Support Trust: 0800 787 254.