The policeman who fatally shot Yamatji woman JC testified at an inquest that he was promoted to senior constable following his 2021 murder trial, having been previously stood down from duty for approximately two years.

Brent Wyndham, a constable during the 2019 shooting, began his testimony at the coronial inquest into JC's death in Geraldton on Thursday.

He was the first police officer in a century to be charged with murder, but was acquitted of both murder and manslaughter at the 2021 Supreme Court trial.

State Coroner Ros Fogliani is investigating the circumstances of JC's death, including the actions and policies of the police and healthcare provided to the 29-year-old before the shooting.

Sen. Const. Wyndham said he was promoted to first-class constable in 2017, five years after finishing his probation.

He served in Broome for a year before returning to Geraldton in 2017.

After the shooting, he was initially stood aside and then formally stood down when charged with murder later that year.

Following his acquittal in 2021, he was then promoted to senior constable upon his return to duty.

Police were on the scene for 44 seconds, and Sen. Const. Wyndham for 16 seconds, before he fatally fired his weapon after repeatedly demanding that JC drop their weapons - a pair of scissors and a 30cm knife.

In his testimony, Sen. Const. Wyndham described how he exited his vehicle and moved towards JC.

He said JC turned towards him and stepped back twice, prompting him to issue four commands: "put the knife down," "get on the ground," "you're under arrest, get on the ground," and "put the f..... knife down," before discharging his firearm.

He expressed fear when JC stepped back and did not comply.

"I felt scared because she was not listening to what I was saying and I've got a gun pointed at her," he said.

"I thought I was going to get stabbed."

Sen. Const. Wyndham explained that use of force training required considering various factors, such as whether the person is armed, their aggression level, proximity to others, and potential mental health or substance abuse issues.

However, he admitted he could not recall if he considered JC's mental health state before shooting her.