A murder-accused policeman who fatally shot an Aboriginal teenager during an outback arrest attempt says he was trained to pull the trigger until an offender is incapacitated.

Constable Zachary Rolfe, 30, contradicted other officers’ evidence by saying he was sent to Yuendumu, 290km northwest of Alice Springs, to arrest Kumanjayi Walker, 19.

Rolfe has pleaded not guilty to murdering the teen on November 9, 2019 after he was stabbed with a pair of scissors.

The constable fired three shots into Mr Walker’s back and torso as he resisted arrest in a dark room at his grandmother’s home.

Defence lawyer David Edwardson QC called Rolfe to give evidence at his trial in the Northern Territory Supreme Court on Wednesday.

The former soldier described Mr Walker as a “high-risk offender, extremely violent, who was willing to use potentially lethal weapons against police”.

He also said he was told by a superior twice that his “mission” in the remote community was to arrest the teen after he violently threatened two other officers with an axe.

The evidence contradicts testimony by Sergeant Julie Frost that she ordered Rolfe and three other officers to arrest Mr Walker the next morning, when he was likely to be sleeping and could be taken into custody easily.

Asked about his NT police force training, Rolfe said he was instructed to shoot when an offender in close proximity was attacking with an edged weapon.

“If someone is threatening us with an edged weapon our first response was to go for our firearm unless that was impossible,” he said.

“You shoot until the offender is incapacitated no matter how many rounds that takes.” 

He said the edged weapon attack exercise was called a “shove and shoot drill”.

“Only draw your firearm if you are prepared to pull the trigger,” he said, when asked what the training entailed.

He said police were also taught that if an offender is 6.4 metres or closer they could attack before an officer had time pull out their firearm.

“If the offender is on top of you cannot assess the situation,” he said.

Asked what incapacitated meant, Rolfe said: “The way I was taught it is that a person no longer has the ability to do what they were doing before”.

Rolfe was composed in the witness box, speaking calmly and often addressing the jury directly as he explained his job as a constable.

Mr Walker died about an hour after Rolfe’s second fatal shot ripped through his spleen, lung, liver and a kidney. 

The Crown has conceded the first shot, fired while Mr Walker was standing and wrestling with Sergeant Adam Eberl, was justified.

But it says the second and third shots, which are the subject of the murder charge, went “too far”.

Prosecutor Philip Strickland SC says Rolfe and his team were “intent” on finding Mr Walker after watching a video of the so called “axe incident” on November 6.

They found the teen about 15 minutes after leaving the local police station where Sgt Frost has said she handed the men a printed page outlining the approved arrest plan for November 10.

Rolfe shot Mr Walker about a minute later during a scuffle as he and Sgt Eberl attempted to handcuff the teen.

Mr Walker first became an arrest target after breaching a court order by removing an electronic monitoring bracelet and fleeing an alcohol rehabilitation clinic in Alice Springs to attend an uncle’s funeral.

The court has also heard Yuendumu community leaders had given an undertaking to bring Mr Walker to police after the funeral on November 9.

The trial continues.

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