Constable Zachary Rolfe, 30, has contradicted senior officers' evidence by saying he was specifically 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 in the shoulder 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.
The former soldier, who served in Afghanistan, said he first became aware of Mr Walker two days earlier in Alice Springs when the teen was listed as an "active arrest target for breach of parole and assault police".
"I characterised him as a high-risk offender, extremely violent, who was willing to use potentially lethal weapons against police," he told the Northern Territory Supreme Court on Wednesday.
Rolfe said he viewed body-worn camera footage of the so-called "axe incident" which showed the two officers freezing in "an extremely, potentially deadly situation".
He said it appeared to have been "swept under the rug" and that he alerted two senior officers to the danger Mr Walker potentially posed.
"This is the kind of incident that we should all be alerted to because Yuendumu is three hours from Alice Springs.
"This offender was, potentially, a risk to Alice Springs members."
He and about six other officers later searched for Mr Walker at a camp in Alice Springs but did not find him.
Two days later a supervisor ordered Rolfe and three other officers from the specialist Immediate Response Team to go to Yuendumu.
Rolfe told the court the superior officer told him twice that his "mission" in the remote community was to arrest the teen.
But senior police have told the trial Rolfe's team was ordered to assist local officers with general duties and carry out a highly visible patrol and gather intelligence about Mr Walker's location.
The court has heard the approved plan was to arrest Mr Walker at 5.30am on November 10, when he was likely to be sleeping and could be taken into custody easily.
Rolfe was composed in the witness box. He spoke calmly and often addressed the jury directly as he explained his job as a constable.
Asked about his seven month NT police force recruit training course, 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 only draw your firearm if you are prepared to pull the trigger.
"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".
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".
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".
Rolfe and his team found Mr Walker 15 minutes after they left the Yuendumu police station on November 9. Rolfe fired his first shot about a minute later.
Mr Walker died about an hour after Rolfe's second fatal shot ripped through his spleen, lung, liver and a kidney.
The court has heard expert evidence that Mr Walker was pinned to the ground by Sgt Eberl and was a "low threat" when Rolfe pulled the trigger the second time.
Other expert witnesses have said the duo should have never gone into the house and Rolfe had not acted as he had been trained.
The trial continues on Thursday.
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