The man, Steven Freeman, had died in the Alexander Maconochie Centre in May 2016, about a year after he suffered serious injuries during an assault in his cell at the prison in April 2015.

The death sparked a coronial inquest which is expected to report back in April this year, as well as an independent inquiry into his treatment inside the prison by former federal integrity commissioner Philip Moss.

It was one of a series of incidents marring the prison's management and reputation in recent years including escapes, assaults and a prisoner being accidentally released.

Questions remain about the prescribing of methadone to him two days before he died, an issue being investigated by both the inquest and a separate inquiry by the Health Services Commissioner.

But corrections minister Shane Rattenbury has confirmed an investigation into the assault on Mr Freeman about a year before he died has been closed.

He said there had been "extensive discussions" between the government and Mr Freeman's family and representatives, but after two attempts by police to investigate the assault, it had been closed.

In his report on the inquiry into Mr Freeman's treatment, Mr Moss wrote of concerns the original police investigation of the assault was lacking, including in failing to ask for records showing swipe card access to his cell three times in the minutes before he was found seriously injured.

It is understood the assault investigation was also hampered by an apparent lack of CCTV footage, an issue Mr Rattenbury said was being addressed through a wide rollout of new cameras in the prison, footage of which was already helping prosecute assaults inside.

Winnunga Nimmityjah health service executive officer Julie Tongs, who has closely supported Mr Freeman's mother, Narelle King, and sat on a committee overseeing the Moss review implementation, said progress was being made.

But she said there was "still a way to go yet" before all the recommendations of the Moss inquiry were implemented, but the new cameras, which were not in place when Mr Freeman was assaulted, were a good thing.

Ms Tongs also said she and Ms King had met with ACT Chief Police Officer Justine Saunders about the assault.

"My understanding is that the information was handed to the [Director of Public Prosecutions], not as soon as we would have liked, but it did happen," she said.

"But they were of the view the information was inconclusive and they'd reached the end of the line as far as the investigation goes."

But Ms Tongs said she remained "optimistic" that in coming years somebody with more information may come forward to authorities about the assault.

"Even though it's cold now, if at any time in the future someone with credible information comes out, they can reopen the investigation," she said.

Ms Tongs also said Mr Rattenbury "should be congratulated" for the progress to date, particularly brining Winnunga's services into the prison for indigenous inmates to get more appropriate services.

But she said more work was needed on information sharing between Winnunga and justice health services, as the Aboriginal health service maintained electronic records, but justice records were paper-based.

Overall, she said that there had been progress on improving the prison and its services since the Moss review, but there were "still things that need to be addressed along the way".