Cleveland Dodd was found unresponsive inside a cell in the trouble-plagued youth wing of a high-security adult prison in the early hours of October 12, 2023.
The 16-year-old was taken to hospital in a critical condition and died about one week later, causing outrage and grief in the community.
Material about Casuarina Prison's youth wing was among late evidence presented to an inquest. (Aaron Bunch/AAP PHOTOS)
Counsel assisting Anthony Crocker on Wednesday told the Perth court a slew of new information had been received overnight from the justice department's lawyers.
It included disclosure of a previously unknown management structure, staff statements and material concerning operations at Casuarina Prison Unit 18, along with a proposed closure date that was not adhered to.
"It is staggering to think that no one before yesterday thought that was germane to court," he said.
Coroner Philip Urquhart agreed with Mr Crocker as he expressed his frustration and dissatisfaction with the material being "dumped" on the court during the third week of the hearing.
He said it was likely to have impacted the questions asked of witnesses who had already appeared and the evidence collected from them.
"I am very, very concerned about this," he said.
"Someone is at fault here and I want to know why it was the court did not receive this."
A department lawyer, David Leigh, said the legal team had received a "huge quantity" of material and it was working hard to find relevant information in it.
Mr Leigh said he would seek further information on the matter and provide it to the court later in the day.
Cleveland Dodd died a week after being found unresponsive in his cell. (HANDOUT/SUPPLIED)
Mr Urquhart in April put the department on notice as the inquest's April sitting concluded after it failed to provide requested information.
He said his preliminary observations of the evidence before the court was Unit 18 was "unliveable, disgusting and inhumane".
The coroner previously heard Cleveland made eight threats to self-harm and numerous requests for medical treatment and drinking water in the hours before he was discovered in Unit 18.
He had covered a CCTV camera in his cell with tissue paper, blocking the view of correctional staff monitoring him from a control room, but it wasn't uncovered until they were fighting to save his life.
Cleveland was found at 1.49am and a code red alert issued two minutes later as staff tried to revive the teen.
Paramedics arrived at 2.06am but did not get access to Cleveland, who was found to be in cardiac arrest, for nine minutes.
The teen was partially revived and taken to hospital but suffered a brain injury due to a lack of oxygen.
He died, surrounded by his family, on October 19.
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