Queensland police were unable to charge Hannah Clarke's estranged husband despite his "disgusting" abduction of one of their children just months before he killed the family, an inquest has been told.
WARNING: This story contains content that readers may find distressing.
Rowan Baxter murdered Hannah Clarke and their children Aaliyah, 6, Laianah, 4 and Trey, 3, while they were on their way to school by throwing petrol in their car and setting it alight on a suburban Brisbane street on February 19, 2020.
An inquest into the murders has heard how Baxter abducted Laianah after taking the children skateboarding at a park.
Giving evidence, Brisbane doctor Julie-Ann Humphries told the inquest she witnessed how Baxter appeared to be "on a mission" when he took the four-year-old on December 26, 2019.
Earlier, the inquest had been told Ms Clarke had been walking across the road with the two other children at the time when Baxter had asked her if he could have the children for the night.
When she disagreed, he suddenly took off with Laianah.
Dr Humphries said she had been cycling along Oxford Street in Bulimba when she saw Ms Clarke with two children who were very distressed.
"The children were crying and screaming out, 'no, stop' and a man and a small child were walking very quickly towards a blue sedan,'' Dr Humphries told the inquest.
"He entered the car with the child on his side … and as he was entering the car he unfortunately bumped her head on the way into the car. He started the car and drove off in quite a hurry.
Dr Humphries said she told nearby police officers she had witnessed something that looked like "child abduction".
Following Dr Humphries's testimony, counsel assisting Jacoba Brasch QC called Detective Sergeant Derek Harris who had received a "child harm" referral about the incident.
He confirmed that after examining the matter he could not investigate, despite describing the act as "disgusting".
"There was no family law court order. There was no child protection order in place to stop Rowan from legally having access to the children," Detective Sergeant Harris told the inquiry.
"But unfortunately, it was not something investigators can progress. I looked at it and it wasn't a crime."
'The criminal code is the criminal code'
Detective Sergeant Harris said he reviewed the matter again on January 1, and by that time Laianah was back with Ms Clarke and the domestic violence order had been taken out.
He acknowledged he had not been made aware that another officer had deemed the couple were "high risk".
But he stated even if he had been told that, it would not have changed his assessment.
"It was done to cause maximum impact to Hannah … it was disgusting … but the criminal code is the criminal code."
Sergeant Harris confirmed he had referred the abduction matter to the State Child Safety Department and had no more involvement in the incident.
He agreed that there were changes that could be made to police training, resources and powers to help stop domestic violence.
He confirmed that powers to investigate telephones would be helpful after Dr Brasch referenced how Baxter had been undertaking internet searches about deleting data from his iPhone.
"More powers that make an investigation easier is always welcomed as long as they don't inhibit people's privacy,'' he said.
He called for education on domestic violence to be presented to children from primary school onwards.
Coroner Jane Bentley released police body camera vision of Baxter and Ms Clarke being pulled over by police for being in an unregistered vehicle.
In the video, Baxter can be heard blaming Ms Clarke for him driving an unregistered vehicle.
The officer is heard detailing a previous offence by Baxter relating to him driving an unregistered and uninsured vehicle in 2016.
Baxter replied: "Which would be the same one what she's done again."
Baxter took his own life beside the burning car containing his children.
Ms Clarke died from her burns shortly afterwards in hospital.
