The Kamilaroi-Dunghutti man, also known as Dougie, died on August 16, 2021, from two perforated duodenal ulcers less than 24 hours after being discharged from Dubbo hospital, in western NSW.

He went to the emergency department on August 14, describing "10 out of 10 pain" and a tearing or popping sensation in his abdomen.

The inquest has been examining whether racism and bias influenced the treatment of the 36-year-old father and grandfather.

Emergency doctor Sokol Nushaj said he misdiagnosed Mr Hampson Jr with the drug-related condition cannabinoid hyperemesis syndrome (CHS).

Dr Nushaj said "coginitive bias" influenced the error, as he had treated other patients with the syndrome and recognised Mr Hampson Jr's symptoms of agitation and pain.

But the senior doctor acknowledged he didn't have the key symptom of vomiting.

"It is a matter of deep regret," Dr Nushaj told the coroner last week.

In the final days of the inquest, Dougie's family described their deep and ongoing torment.

"He was meant to walk into the Dreamtime as an aged and frail man, warm in his bed, surrounded by his loved ones, leaving behind a lifetime of memories and happy times," Ms Chatfield said, her voice wavering, on Thursday.

"Instead, he was a young man and died alone in unimaginable pain and suffering because of a system that failed him."

His mother, Lydia Chatfield, described herself as "broken".

She said she often saw her son in her dreams.

"I hold onto you and breathe you in and you wonder what all the fuss is about, like you haven't really left me," Ms Chatfield said.

A slide show played to the court showed Dougie as a child, riding a bike, running through a sprinkler, grinning under a shimmering Christmas tree and snuggled in spotty pyjamas.

Videos showed him as an adult holding his own children, playing with young relatives, dancing and laughing.

Ricky Hampson Sr said the family want change so all First Nations people can be safe in the healthcare system.

"When systemic racism in our institutions is taking black lives in one way or another, it has a ripple effect that destroys so many of our lives," he said.

"It enforces our people's lack of trust within these institutions and the system itself."

Counsel assisting the inquest Simeon Beckett SC said it would be open for the coroner to find bias played a role in Mr Hampson Jr's death.

"The diagnosis Mr Hampson Jr had CHS was influenced by the fact that he had used cannabis and Dr Nushaj had seen many Aboriginal people with that syndrome," Mr Beckett said.

The inquest is due to close on Friday.

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