An inquest into the death of mother-of-three Kelly Wilkinson has been told it was "not appropriate" for an arresting officer to grant bail to Johnston who had been identified as a "high" domestic violence risk.
Ms Wilkinson, 27, was later repeatedly stabbed, doused with petrol and set on fire by Johnston at her Arundel home on the Gold Coast.
The police response to Ms Wilkinson's domestic violence complaints has come under scrutiny at the Southport inquest into her death on April 20, 2021 which opened on Tuesday.
Counsel assisting Sarah Lane told Deputy State Coroner Stephanie Gallagher the inquest would look into whether police acted in accordance with procedures and policies.
Johnston had been subject to a domestic violence order at the time of the murder and was on bail accused of sexually assaulting Ms Wilkinson.
He had been charged with four counts of rape and should have been required to make a bail application before a magistrate, Detective Inspector Sue Newton told the coroner.
She said the offences ensured Johnston was in a show-cause position where he had to prove his detention was not warranted.
Johnston was instead granted police bail soon after being charged on April 11, 2021.
Testifying about the police ethical standards command's probe into Ms Wilkinson's case, Det Newton said it was inappropriate for the officer who arrested Johnston to decide whether to grant bail.
"The Bail Act ... wasn't being followed at all times, is that something you looked at?" Ms Lane asked.
"Yes," Det Newton said.
Ms Wilkinson and Johnston's first contact with police was about three weeks before the murder.
Johnston initially contacted officers in anticipation Ms Wilkinson would accuse him of rape, Det Newton said.
Ms Wilkinson was designated as a "high-risk aggrieved" person, while the Gold Coast Domestic Violence Prevention Centre urged police to produce a "high-risk response" to her being in danger.
"(Police) put a high-risk flag on her name and residence," Det Newton said.
Ms Wilkinson contacted police on April 1 to report Johnston had breached a protection order after he got a third-party to contact her about returning his property and getting access to the children.
Officers were tasked with responding to Ms Wilkinson's complaint as a "lower priority" job.
There was no indication her complaint should have been treated as urgent, but the officers making the decision would not be aware of her "high risk" of domestic violence, Det Newton said.
The coroner responded: "You are going to have to explain that to me".
It would take more than a week to provide evidence about that decision, the police commissioner's barrister Michael Nicholson told Ms Gallagher.
Ms Wilkinson was later accused of "cop shopping" by police, who did not act on her complaints days before her badly burnt body was found outside her home.
The officer who made the comment was later the subject of a disciplinary interview, Det Newton said.
No officer was disciplined as a result of the case but two were given remedial training, she added.
Johnston, a former US marine, later entered Ms Wilkinson's home wearing black clothing and a black mask while carrying a backpack with a hatchet, duct tape, zip ties and sedatives.
Ms Wilkinson's body was found outside her home and her killer was found nearby after he collapsed and suffered burns.
Johnston was jailed for life in March 2024 after pleading guilty to murder.
Members of Ms Wilkinson's family attended the inquest on Tuesday but did not comment.
Ms Wilkinson's sister Danielle Carroll said outside court in 2025 that "there's still a lot of information we don't know".
"Hopefully we can learn something and move forward and make the world a bit safer for other victims," she said of the inquest.
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