An Aboriginal teenager was "in many respects the author of his own misfortune" when shot dead by a Northern Territory policeman, his murder trial has been told.
Senior police have "thrown everything at Zachary Rolfe" to justify charging him with murdering Kumanjayi Walker without "any meaningful investigation", defence lawyer David Edwardson QC says.
Constable Rolfe, 30, has pleaded not guilty to murdering Mr Walker as he resisted arrest in Yuendumu, 290km northwest of Alice Springs.
Mr Edwardson QC told the Northern Territory Supreme Court on Wednesday the death of the 19-year-old on November 9, 2019 was a tragedy.
"A young man has lost his life and a young courageous police officer has been charged with the most serious charge known to criminal law," he said during his closing address.
He said his client was arrested within four days of the shooting without a "meaningful or proper investigation".
"That, you might think, is a disgrace," he said.
"The executive of the NT police force and those they have deployed to justify these charges have thrown everything at Zach Rolfe because it was a decision that should never have been made."
He said Mr Rolfe's prosecution was the NT police force executive attempting to "justify what was unjustifiable".
Mr Edwardson also took aim at the NT police force's treatment of the officer-in-charge at Yuendumu, Sergeant Julie Frost, saying the NT police force had "thrown her under the bus" and she was also a "victim of this appalling investigation".
"They had 841 plus days since the decision was made to charge Zach Rolfe and actually produce a case," he said.
"The Crown produced 40 witnesses to support the narrative that Rolfe, a police officer, was guilty of murder.
"We say they have not come close."
Mr Edwardson said almost all witnesses had confirmed that Mr Rolfe had acted as he was trained and his response when he fired three shots was reasonable and proportionate.
"Let us be brutally frank about this young man," he said referring to Mr Walker.
"The truth of the matter is that he had a lengthy and violent criminal history."
He said Mr Walker had threatened two other police officers with an axe on November 6 "in an extraordinarily dangerous and confronting manner".
"Which of itself would have justified him being shot," he said.
"Worse still, on November 9 he deployed a lethal weapon, namely the scissors, but this time he stabbed Zach Rolfe before turning his attention to (Sergeant Adam Eberl, then a constable).
"He might have been a young man and for that reason if nothing else, this case is tragic but nonetheless he was dangerous and violent and in many respects the author of his own misfortune."
Mr Edwardson said when Rolfe moved to arrest Mr Walker it was "in accordance with the command he was given by the warrant".
"At that very moment Kumanjayi Walker suddenly and without notice deployed a previously hidden pair of scissors and stabbed Constable Rolfe," he said.
"If Walker had hit his carotid artery Zachary Rolfe would be dead."
Mr Edwardson described Mr Walker's attack as a "spontaneous ambush".
"When Kumanjayi Walker deliberately and, I suggest, viciously, tried to stab both officers ... the only appropriate response was to draw his firearm and pull the trigger ... until the threat was removed," he said.
He said Rolfe had acted in good faith, the reasonable performance of his duties and in the defence of himself and Sgt Eberl.
"It is for the prosecution to negate each of the three defences beyond reasonable doubt and they simply have not."
The jury is expected to start deliberating after Justice John Burns makes his final address on Thursday.
