The inquest into the death of Dunghutti man David Dungay has begun at Sydney's Downing Centre court.
David Dungay Jr was weeks away from release after serving an eight-year sentence, and the Deputy State Coroner Derek Lee will look into the actions of prison staff in the lead up to his death on December 29, 2015.
It is understood the 26-year-old, who was diabetic, was told by prison guards to stop eating biscuits.
When he refused, he was moved from one cell to another, held face down by prison staff, and injected with the drug midazolam.
Distressing scenes of Mr Dungay's final moments were shown in court.
'I can't breathe'
In new podcast series 'Breathless', co-produced by The Guardian and 2SER, family members talk through what they have seen on video footage they had been shown of Mr Dungay being restrained, his neck pressed on the lip of the bed frame.
“My uncle’s saying ... I can’t breathe, I can’t breathe. They’re saying you’re talking so you can breathe,” David's nephew Paul Silva tells 'Breathless'.
He says his uncle's mouth was full of blood.
Outside Downing Centre Court in Sydney on Monday, Mr Dungay's mother Leetona thanked her supporters.
“I want justice for my son,” she said.
“I’ll be strong in and out of this court every day.”
Leetona Dungay has previously said she believes there has been a cover up over David's death.
"I'd like those people who put my son in a black bag be accountable Why and who done it? And I'd like them to come forward and be honest, no cover up, come forward for your guilt in what you done," Leetona Dungay told NITV News last year.
In the Counsel Asssisting the Coroner Jason Downing's opening address, regular difficulties relating to Mr Dungay's diabetic treatment in jail are detailed, as well as how Mr Dungay had been transferred to the mental health facility within Long Bay jail on November 23.
On the day he died, Mr Dungay "reported feeling much better after having spoken on the phone to his mother".
Throughout December 29, Mr Dungay's blood sugar level was taken multiple times throughout the day by a nurse.
He had bought the packet of biscuits on the way back from exercising in the yard.
"It is not entirely clear who raised a concern about the possible effect of eating the biscuits on MR Dungay's blood sugar level."
At 2.41pm, after orders to cease eating the biscuits, officers entered the cell - one with a riot shield.
"In the course of Mr Dungay being restrained in the prone position on the bed of cell 71, with officers above him and seemingly placing weight on him, he began to scream 'I can’t breathe'."
Moved to another cell, "Mr Dungay continued to scream that he could not breathe".
In the second cell, "he was placed onto the bed face down and again restrained by the IAT officers placing weight onto him".
He became unresponsive around one minute after receiving the midazolam injection. Resuscitation attempts were unsuccessful.
Key issues the inquest will cover will be how Mr Dungay was assessed and managed after he returned from the exercise yard, particularly the decision to move him between cells and processes around enforced tranquilisation.
"There is evidence that in the past, where there were difficulties in dealing with Mr Dungay, particularly in relation to his blood sugar levels, Justice Health nurses, other Aboriginal inmates and an Aboriginal Delegate were able to speak to him and calm him down."
Outside the court, Greens MP David Shoebridge encouraged supporters to help the extended family cover the high cost of travelling to Sydney for the inquest.
They had requested financial support from the NSW government to make the trip from Kempsey on NSW's mid-north coast, but according to Mr Shoebridge they were only notified on Friday that this would not be provided.
“It took a direct intervention to get the bare accommodation costs for David Dungay’s mum Leetona, but she needs the support of the rest of her family who don’t know where the funds will come from," Mr Shoebridge said in a statement.
“You’re not equal before the law if you can’t even get to court," he said.
“David Dungay died in jail after being restrained and tranquilised. He died in a government institution at the hands of a criminal justice system that failed him, and now that same system is failing to look after his family.”
Black Rights Matter activist Hank Newsome also attended the inquest on Monday to support the Dungay family.
The inquest is expected to run for two weeks.