The murder trial of Northern Territory police officer Zachary Rolfe has heard he was likely struck with the sharper blade of the scissors used on him by Kumanjayi Walker before he fatally shot the 19-year-old.
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.
Constable Rolfe, 30, fired three shots at Mr Walker during an attempted arrest in Yuendumu in November 2019, with the first shot fired after Mr Walker stabbed Constable Rolfe in the shoulder with a pair of medical scissors.
Constable Rolfe has pleaded not guilty to murder, as well as two alternative charges, arguing in part that he was defending himself and a fellow officer from an edged weapon when the shots were fired.
On Thursday, as the trial nears the end of its third week, the NT Supreme Court heard from a forensic chemist with the Australian Federal Police.
Timothy Simpson told the court he was asked by investigators to analyse the textile damage on the uniforms worn by Constable Rolfe and Sergeant Adam Eberl during the incident.
He said his initial visual inspection of the clothing — which was undertaken before investigators informed him of the cause of the damage — indicated the tears in the fabric on Constable Rolfe's shirt were likely the result of a single blade.
"In my head, the implement that I was looking for was something similar to like a small blade, [a] small folding knife, like a Swiss army knife sort of blade," he said.
Mr Simpson said he was surprised to later learn the object used was actually a pair of scissors.
"When I was presented with the scissors, I was l like 'I'm going to have to think about this a bit more, about how that implement could then be used to create that damage'," he said.
The court heard Mr Simpson then conducted an experiment using a piece of pork belly wrapped in police clothing, to simulate the potential effects of the scissors.
He said the experiment showed the less-pointed blade on the scissors could not penetrate the clothing, whereas the sharper blade could.
"When the [sharper] blade was used in a stab and drag action, the implement could not be excluded [as the cause of the textile damage]," he said.
The court has previously heard the scissors left a 3mm wound on Constable Rolfe's shoulder that did not require stitches.
Under cross-examination from the defence, Mr Simpson said the sharper blade went about three quarters of the way into the pork belly using a moderate level of force.
"Not all the way to the hinge, but the majority of the blade," he said.
Asked by the prosecution if the use of pork belly was the best way to replicate a human shoulder, he said a pig's shoulder might be more accurate, but that pork belly was the only "validated medium" in his profession.
Constable Rolfe a 'good marksman', court told
The court also heard further evidence on Thursday from Sergeant Lee Bauwens, who helped set up the specialist police unit from which officers were deployed to Yuendumu on the day Mr Walker was shot.
He agreed with Crown prosecutor Philip Strickland SC that Constable Rolfe, who was a member of the Immediate Response Team (IRT), was a "good marksman" who got a perfect score during a shooting qualification exercise several months before Mr Walker's death.
Under cross-examination from the defence, Sergeant Bauwens was asked about the circumstances in which an officer might use their firearm.
"If somebody's brandishing a chopstick, you don't pull out your gun, do you?" defence barrister David Edwardson QC asked.
"Generally, no," Sergeant Bauwens replied.
"On the other hand, if they produced an edged weapon which is potentially lethal, then you're told you're entitled to deploy your weapon and you have to, if necessary, be prepared to pull the trigger?" Mr Edwardson said.
"That's correct," he replied.
Sergeant Bauwens told the court that police are trained to keep firing their gun "[until] the threat no longer exists."
The trial before Justice John Burns continues tomorrow.