A Northern Territory policeman accused of murdering an Aboriginal teenager armed with scissors was trained that an “edged weapon equals gun”, his lawyer says.

Constable Zachary Rolfe, 30, has pleaded not guilty to the shooting murder of Kumanjayi Charles Arnold Walker during a failed arrest attempt on November 9, 2019.

The 19-year-old died after he was shot three times in his mother’s home while he was holding a pair of scissors in the remote community of Yuendumu, 290 kilometres north-west of Alice Springs.

Defence barrister David Edwardson QC told the jury that police training required Constable Rolfe to draw his pistol and “incapacitate” when threatened by a person armed with a blade.

“He had been stabbed and his partner was locked in combat with an armed assailant with predisposition for violence,” he told the Supreme Court in Darwin on Tuesday.

“He was taught, trained and drilled as a member of the NT police force that edged weapon equals gun.

“In other words, when an officer is confronted with an edged weapon, the appropriate response is to draw your weapon and be prepared to use it.”

Constable Rolfe did.

He fired three shots into Mr Walker, who had a significant criminal history that included violence, assaults against police and escaping custody.

About a week before he died, Mr Walker removed an electronic monitoring device and fled an Alice Springs alcohol rehabilitation centre so he could attend a relative’s funeral.

He also threatened police in Yuendumu with an axe as he ran from them a few days before he died.

Constable Rolfe’s first shot is not the subject of the murder charge. It relates to the second and third shots, which the prosecution says were not legally justified.

“It is the defence position that Constable Rolfe, having been stabbed by a known violent offender and having lawfully shot him once, was justified in continuing to defend his mate and fellow police officer,” Mr Edwardson said,

Earlier, prosecutor Philip Strickland SC said Constable Rolfe disobeyed a senior officer’s instructions given 22 minutes before the shooting to “gather intelligence” in preparation to arrest Mr Walker the next morning.

“The accused and other (officers) chose to ignore that operational plan,” he said.

“When they left Yuendumu Station at 7.06pm, they were intent on finding and arresting him that evening.”

After Constable Rolfe shot him, Mr Walker called out for his mother and moaned as the officers handcuffed him. He also threatened to kill them.

In the dark room as Mr Walker bled on to a grubby mattress on the floor, Constable Rolfe told his partner: “He was stabbing me. He was stabbing you”.

Mr Strickland suggested to the jury that Constable Rolfe may have said those words “because he knew he had gone too far”.

“He knew the shots were not necessary or reasonable. He knew everything he had done was captured on the body worn video,” he said.

“In short he said those words to justify what he’d done.”

Mr Walker died at 8.36pm after the officers had moved him to the local police station and “done the best they could to save his life”.

Either the second or third shots “fatally damaged” his spleen, kidney and right lung.

“He intended to kill Kumanjayi Walker, or cause him serious harm,” Mr Strickland said of Constable Rolfe.

The trial continues on Wednesday.

-AAP