The number of Indigenous people who have died in custody in Australia has hit the highest level since records began in 1980.

New data from the Australian Institute of Criminology showed 33 of the 113 people who died in custody in the 12 months to June this year were Indigenous, up from 24 compared to the previous corresponding period.

Aboriginal and Torres Strait Islander people are disproportionately represented in the criminal justice system, making up more than one-third of all prisoners, despite being less than four percent of the country's population.

The figures come more than three decades after a landmark inquiry into Indigenous deaths in custody, which made hundreds of recommendations.

Of the 33 Indigenous deaths in custody between last July and this June, 26 died while in prison custody, an increase from 18 in the previous 12-month period. One died in youth detention, and all except one were male.

The remaining six Indigenous deaths in custody occurred in police custody, where individuals died while being detained or while the police were attempting to detain them.

The main cause of Indigenous deaths was categorized as self-inflicted followed by natural causes, with hanging being the cause in eight of the fatalities.

The Australian state of New South Wales recorded the highest number of Indigenous deaths in prison custody with nine, followed by Western Australia with six. Queensland, South Australia, and the Australian Capital Territory each reported three deaths.

The NSW state coroner recently described the rising number of Indigenous deaths in custody in her state as a profoundly distressing milestone. In October, Magistrate Teresa O'Sullivan emphasized that the upward trend was not just mere statistics and required independent and careful scrutiny, respect, and accountability.

The average age of Indigenous individuals who died in custody was 45 years, with 11 of those deceased awaiting a sentence.

University of Melbourne associate professor of criminal law Amanda Porter communicated to the Australian Broadcasting Corporation (ABC) that the figures reflect a national crisis demanding leadership and political action. Ms. Porter noted that little has improved since the royal commission in 1991 aimed at confronting this crisis.

Since the royal commission, 600 Indigenous people have died in custody, including six in youth detention, according to the report.