Winnunga Nimmityjah chief executive Julie Tongs said the Indigenous community already held a problematic view of the justice system, and the bashing acted to "confirm deeply held suspicions and concerns within the community about the administration of justice".

"There's something not right with this. It's very very wrong that a young man could be taken from the watchhouse at 3 o'clock in the afternoon and end up in the intensive care ward three hours later," she said.

Ms Tongs wrote to Justice Minister Shane Rattenbury this week asking him to hold an independent inquiry.

Mr Freeman is a client of the Aboriginal health service. Ms Tongs said the family was very distressed and did not yet know to what extent Mr Freeman, who has woken from a coma, would recover. His mother had not left her son's side in hospital.

"She is just absolutely devastated and she doesn't want to any other parent to go through what she is going through at the moment," Ms Tongs said.

Mr Freeman, 24, was charged on Monday, April 27, in relation to alleged police pursuits and car thefts in NSW and the ACT, and was remanded in custody to appear in court on Tuesday, April 28. But within a few hours of being transferred to the Alexander Maconochie Centre, he was critically injured.

ACT Police are still investigating, but Ms Tongs said the case demanded a wider inquiry.

"The fact that such a serious assault has been committed on an Indigenous remandee within the first two to three hours of his incarceration raises serious questions about the induction arrangements in place at AMC and the extent to which the AMC has met its duty of care to Steven," she wrote to Mr Rattenbury.

"This incident warrants a much broader independent inquiry into all of the circumstances of and surrounding Mr Freeman's treatment and management from the time of his departure from the Magistrates Court until his hospitalisation subsequent to the assault he suffered while in the care and custody of the AMC."

Mr Freeman was "always respectful and a nice young man but obviously a troubled young man that stole cars, but was never ever violent that I'd seen", she said.

Ms Tongs said the system had failed him, and called on the prison to explain procedures for ensuring remandees' safety, checking whether they were at risk and inducting them into the prison system.

"You're not there to get a smack on your hand, but you're not there to be bashed to within a minute or your life either," she said. "Nothing seems to add up at all around this, and to happen in such a short space of time when other as other detainees were there, someone must have seen something."

Mr Rattenbury said Corrective Services had held a "post-incident debrief" to assess actions taken by staff before, during and after the incident.

"I am seeking preliminary advice on any issues that may have been identified by ACT Corrective Services and consider what further investigation may be required," he said. "I understand the community's concern regarding this issue."

Prison management had held a meeting with Indigenous detainee delegates, the Indigenous official visitor and the Indigenous liaison officer, he said.

Just over 20 per cent of prisoners (75 of 350) at the ACT prison are Aborigines or Torres Strait Islanders.