That officer, who has had their identity suppressed, has pleaded not guilty to murdering the woman, known as JC at her family's request.
Senior Constable Barker was among eight officers who responded after a report that a person was seen carrying a 30 centimetre knife on Assen Street in Rangeway.
He told the court on Friday that he recognised JC from when he had detained her under the Mental Health Act ten days earlier, after JC called triple zero and threatened to harm herself.
On that occasion, Senior Constable Barker apprehended JC and loaded her unassisted into a police vehicle. He then drove her to Geraldton Regional Hospital and remained there while hospital staff assessed her.
“She gave my hand a squeeze, watched me on the way out and gave me a smile and a wave,” he told the court about leaving JC at the hospital.
Ten days later, Senior Constable Barker responded when JC was stopped by police on Petchell Street, near Assen Street, while carrying a large knife and a small pair of scissors.
On Friday, two other officers that were the first to arrive at the scene gave evidence, and said JC ignored a request to drop the weapons.
JC “never spoke to me, at all. She shrugged her shoulders at one stage and just continued walking”, Senior Constable Kenneth Walker told the court.
Four police cars in total converged on Petchell Street, with three officers exiting their vehicles and confronting JC, who was still carrying the knife and scissors.
One officer ran towards her pointing a loaded, police-issued firearm. The other aimed an unarmed Taser at her, while the third officer, Senior Constable Barker, approached unarmed.
Senior Constable Barker told the court on Friday that he believed talking to JC was the most effective way to get her to drop the knife.
“Guns or a firearm, even a Taser, pepper spray, to me I feel they’re a barrier to communication. I was trying to talk to her to get her to drop it. I was aware there were other officers there to assist me,” he said.
Senior Constable Lucy Cleghorn and Senior Constable Barker stayed inside their vehicle and watched the scene from about 4-5 metres away.
By this time JC had stopped walking away from the officers and was standing in the middle of the road, facing the officer aiming the gun and the officer aiming the Taser.
Senior Constable Barker was approaching to the left-hand-side of JC, with his left hand open and extended, and his right hand by his side, near his gun holster.
Senior Constable Cleghorn told the court she thought Senior Constable Barker had placed himself at risk by approaching unarmed.
“I was afraid for him. From what I could see he was so close to [JC], that I thought he was going to be stabbed. All of my attention, focus went to Senior Constable Barker,” she said.
Neither officer said they saw JC move the moment that she was shot, but said their attention was not focused specifically on her.
However, with the driver’s-side window down, Senior Constable Kenneth Walker said he observed JC was in an “agitated state”.
“It was almost like she was clenching her hand, the knife was slightly moving. I heard someone say ‘drop the knife’. Then I heard a loud crack, which I identified as a gunshot.”
JC was shot by a single bullet, which Senior Constable Barker initially thought was a Taser.
“I remember a pop, crack, and I remember [JC] go slightly backwards to her right … She hit the ground facing away from me,” he told the court.
“Originally, I thought it was a Taser, because someone had said ‘you’re going to get Tasered (moments before)”.
CCTV footage of the incident played to the court shows JC falling to the ground.
The prosecution says it shows conclusively that she did not take a step towards the officers before she was shot.
The trial continues.
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