Constable Rolfe, 30, was a member of the Alice Springs Immediate Response Team, which was deployed for "general support" to the community of Yuendumu - about 300km away - on the night he shot Mr Walker three times in the chest in November 2019.

The officer in charge of that team, Sergeant Lee Bauwens, told the court on Thursday that the team's primary role was to "cordon and contain'' a potential offender outside a house and wait for the specialist Territory Response Group to arrive.

During cross-examination by Constable Rolfe's lawyer, David Edwardson QC, Sergeant Bauwens said it was not always possible to wait for the response group, meaning the response team was able to take what's called an "Immediate Emergency Action".

"If, within the situation we are controlling, if a life-threatening situation would occur within that situation, we are authorised to enter, identify, challenge and - and form an arrest of an offender and save the lives of the person within the stronghold," he said.

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However, Sergeant Bauwens said the response team could plan to enter a house to make an arrest.

"We can only respond to an incident ... we cannot plan to go in there on our own accord. We have to wait for an emergency to develop."

The team also needs to be on a "high-risk" deployment, which it was not at the time of the shooting.

Constable Rolfe and his partner, Remote Sergeant Adam Eberl, entered the house Mr Walker was in about 7.20pm, roughly 15 minutes after they had been deployed, on information from a community member he might be there.

By 7.23pm, Constable Rolfe had shot Mr Walker three times after Mr Walker stabbed him in the shoulder with a pair of scissors in an attempt to avoid arrest.

The court heard earlier in the trial that the Officer in Charge in Yuendumu, Sergeant Julie Frost, had instructed the response team members to conduct general patrols and gather intelligence on Mr Walker's whereabouts before helping a local police officer with his arrest at 5am the next day.

Sergeant Bauwens, however, agreed with Mr Edwardson that Mr Walker was deemed a "high-risk" offender because of an incident three days before where Mr Walker had avoided arrest by running at two police officers with an axe.

Mr Edwardson asked, "So even though it was a general duties, or general support deployment, it was a general support deployment to arrest a high-risk target?"

Sergeant Bauwens replied, "Correct."

The court also heard from Australian Federal Police forensic chemist Timothy Simpson, who had been sent the scissors used by Mr Walker and clothing worn by Constable Rolfe and Sergeant Eberl during the shooting in order to determine how the scissors were used to cause the damage to the clothing.

He told the court he conducted tests that determined that only the pointier of the scissors' two blades was capable of penetrating the fabric worn by the two officers, meaning the scissors would have had to have been open when they were used.

Forensic pathologist Dr Marianne Tiemensma, who conducted the autopsy on Mr Walker's body, told the court earlier this week she believed the scissors had been used with the blades closed as Mr Walker had no injuries to his hands.

She said the scissors when closed were blunt and probably incapable of causing serious injury in the circumstances.

The trial continues.