A Northern Territory Police prosecutor allegedly involved in the death in custody of 24-year-old Warlpiri man Kumanjayi White was allegedly aggressive toward Indigenous workers at a youth centre in Mparntwe/Alice Springs in the past.

NT Police Prosecutor Steven Haig is believed to be one of two plain-clothed officers who restrained Mr White during an arrest last month, after which Mr White died in custody.

Despite numerous questions, NT Police have refused to confirm the officers' identities or stand them down, while being prepared to publicly comment on Mr White's alleged criminal history.

Speaking to National Indigenous Times on condition of anonymity, an employee at a local youth outreach centre recalled an encounter involving Mr Haig and other NT Police officers, who visited the safe space one evening in search of five young people who "potentially could be there".

The employee alleged Mr Haig's behaviour was immediately concerning.

"Our kids were out the back waiting for their dinner; we had 35 kids that night," they told National Indigenous Times.

"I asked him to calm down as this was a safe space for the kids and we wanted it to stay that way. He didn't calm down he got angrier and he... threatened to arrest me 'for intervening with the course of justice'."

The employee said they instead approached another officer wearing a body camera who appeared "calmer and more approachable".

"I explained to him," the youth worker said, "'This aggressive behaviour is not acceptable for a police officer. I know you guys deal with a lot but that doesn't give you the right to act like that.'"

They alleged they then pointed at Mr Haig and said: "He's going to kill someone one day. He's trigger happy."

Multiple media outlets have now identified Mr Haig as being involved in the arrest of Mr White. However, without standing down, he will likely continue to prosecute cases for NT Police in a jurisdiction facing ongoing scrutiny for disproportionately incarcerating Indigenous people.

Witnesses interviewed by ABC and NT News allege an officer placed a knee behind Mr White's head prior to his death.

The NT Independent has revealed Mr Haig was previously the subject of complaints for his forceful arrest of a young Indigenous woman—at the same Coles supermarket where Mr White was detained. A published photo shows Mr Haig with his right leg and knee across the woman's neck.

NT News later identified the woman as 29-year-old Sharon Adamson, who, like Mr White, was reportedly dealing with mental health issues at the time. She is scheduled to appear in Darwin Court on June 16 after Judge Sarah McNamara agreed the hearing should not be held in Alice Springs.

The NT Independent further reported that Mr Haig has "apparently been the subject of previous complaints concerning 'use of force' and other matters".

Following Mr White's death, his grandfather, Warlpiri Elder Ned Jampijinpa Hargraves, said: "We know that he was held down by two police... he lost consciousness and perished. But at the moment we are in the dark about what really happened."

Nationwide protests and vigils have followed, with prominent voices—including Minister for Indigenous Australians Malarndirri McCarthy and Labor MP Marion Scrymgour—calling for an independent investigation into Mr White's death. Both the NT Chief Minister and NT Police have rejected those calls.

National Indigenous Times has asked NT Police for comment regarding Mr Haig's behaviour, his record in the community, and the number of complaints made against him.

NT Police said they would not comment on any of the individuals involved in Mr White's death, nor on any of the aforementioned incidents allegedly involving Mr Haig. A section of the NT Police's "guide to the release of information says: "If information falls within one or more of the following categories, it should be considered for public release: Public safety concerns."

Furthermore, for investigations which involve Police (including off-duty Officers), it states: "In the interests of natural justice, receipt of allegations and complaints alone prior to any preliminary investigation being completed will not be released to the public unless there is an immediate concern for public safety."

Nonetheless, NT Police pointed to previous statements made by the Acting Commissioner, the last of which alleged criminality on Mr White's behalf — despite the late Mr White having no ability to defend himself, and before any investigation was completed. These claims have been criticised and asked to be withdrawn by legal representatives acting on behalf of his family.