Rolfe shot the Aboriginal teenager three times during a failed arrest attempt in Yuendumu, 290km northwest of Alice Springs, on November 9, 2019.
The 19-year-old died on the floor of the local police station 74 minutes after the second fatal shot ripped through the teen's spleen, liver, left kidney and right lung.
The constable has pleaded not guilty to murder, saying he was doing his job and defending himself from a violent offender who had stabbed him in the shoulder with a pair of scissors.
Pathologist Marianne Tiemensma performed an autopsy on Mr Walker's body three days after he died.
She told the Northern Territory Supreme Court on Tuesday that Rolfe's first shot into the right side of the teen's back would not have killed him.
"It did not really travel very far. It just got stuck in a large muscle group ... adjacent to the spine," she said.
"It caused minimal injuries to some structures. Not to the vascular structures. It did not result in excessive bleeding.
"If untreated over time it could cause trouble but in the immediate first hours and days after it was inflicted I do not think it was going to cause a fatal injury."
Prosecutors have conceded the first shot, which was fired while Mr Walker was standing and resisting arrest, was justified.
But they say the second and third shots went "too far" because the teen was "effectively restrained" on the ground by another officer when Rolfe pulled the trigger.
Dr Tiemensma found Mr Walker had a very low blood alcohol level the night he died and an insignificant amount of cannabis in his system.
Asked whether the 10cm long scissors the Mr Walker stabbed Rolfe with could have killed him, she said it was unlikely.
She said the scissors were small and blunt, and the teen would have struggled to generate enough force to penetrate the officer's clothing.
"I don't think these scissors could have caused fatal injury," she said.
Earlier, military surgeon Michael Reade said Rolfe's second shot may not have killed Mr Walker had there been trained medical staff in Yuendumu.
An autopsy found Mr Walker died from breathing difficulties caused by a collapsed lung and blood loss.
Dr Reade said nursing staff at the local clinic may have been able to keep him alive long enough to get him to Alice Springs for lifesaving surgery.
But they had fled the community of about 800 over safety concerns earlier in the day after their homes were broken into the night before.
The trial continues.
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