The scissors used by Yuendumu man Kumanjayi Walker to stab police officer Zachary Rolfe in the shoulder before he was fatally shot could not have caused lethal injuries in the circumstances, a medical expert has told the constable's murder trial.

WARNING: Aboriginal and Torres Strait Islander readers are advised that this article contains an image of a person who has died, used with the permission of their family.

Mr Walker died about an hour after Constable Rolfe, 30, shot him three times during a struggle and attempted arrest inside a house in the remote community in November 2019.

Constable Rolfe has pleaded not guilty to murder, as well as alternative charges of manslaughter and engaging in a violent act causing death.

Government forensic pathologist Marianne Tiemensma told the Northern Territory Supreme Court on Tuesday that she did not believe Constable Rolfe or his partner were at risk of serious injury or death during the struggle with Mr Walker.

Dr Tiemensma, who performed Mr Walker's autopsy, told the court she was also asked by investigators whether the medical scissors used by the 19-year-old had the capacity to cause a "penetrating injury".

She said, in her opinion, the blades of the scissors were closed at the time Constable Rolfe was struck with them, meaning they had a thick blunt tip.

She said body-worn footage showed there was also a "very short window of opportunity for any meaningful attack" and that Mr Walker was "immediately restrained" by officers wearing clothing which would have caused "additional resistance".

"In these circumstances, I don't think that pair of scissors would have caused fatal injury to the carotid artery," she told the court.

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Maybe someone should introduce the good doctor to the work of The Late Mark Brandon "Chopper" READ, or Keithy George FAURE.