In December 2016, 18 months before Edwards murdered his children and then took his life, the children's mother walked into Hornsby police to report three instances of Edwards assaulting Jack and Jennifer.

The report - taken by an 18-year veteran who'd not read the police manual on domestic violence until she gave evidence on Wednesday - mistakenly dubbed Olga Edwards the victim and attributed the start date of the 2015 alleged assaults to March 2016, when Ms Edwards and the children left the family home.

The allegations included that Jack had been punched and kicked for touching his father's iPod and Jennifer was slapped in the face for not going to bed as told.

State Coroner Teresa O'Sullivan is examining the lead-up to Edwards gunning down the two teenagers in Sydney's leafy Hills District in July 2018.

Several allegations of domestic violence against the estranged father were either not recorded properly by police or were not considered by registry staff before he acquired his pistol licence in mid-2017, the inquest has heard.

Senior Constable Brooke Cooper accepted on Wednesday she was also wrong to answer "No" to a question about whether children were a witness or victim of the alleged assaults and to label the matter "domestic violence - no offence".

Sergeant Rodney McCaffery, who was recorded as appraising the report, told the NSW Coroners Court he didn't actually read it but used Sen Const Cooper's verbal account of what had gone on to make his assessment.

He said there wasn't enough evidence to put the accusations to Edwards, describing the mother's report as a "notification" not an allegation or evidence.

Asked if it was enough to at least talk to Jack and Jennifer, he said he wasn't sure what he would have done.

"They were invited to come in ... which is furthering the investigation," he said.

"If there was more evidence, you could go to the home."

Pushed to think of other investigative steps that could have been possible, Sgt McCaffery said Ms Edwards could have been contacted to "ascertain what they intended to do, whether they are going to bring more evidence".

"She'd come to the police for help!" Ms O'Sullivan said.

The silent sergeant was then prodded again to detail what other steps he would have taken.

He agreed it would have been reasonable to ask Ms Edwards for contemporaneous documents to support her claims and have the children come into the station.

He cited "distractions at home" as a reason he preferred to interview children in a police station - drawing questions from Ms O'Sullivan as to why that was better to a familiar environment like their own home.

"Is this a general rule you have?" she asked.

"It's not a rule I have. I don't remember the specifics of that conversation. I didn't know if he (Edwards) was in the picture at the time," the sergeant replied.

"You should've known that!" Ms O'Sullivan said. "If you didn't know that, why didn't you ask?"

Sgt McCaffrey reiterated he couldn't recall the specifics and later said interviewing children in a station wasn't a preference.

The inquest heard after Ms Edwards didn't bring the children into the station to speak with police, as requested, Sen Const Cooper made another note on the file.

"Maybe a premeditated attempt [to] influence some future family court and divorce proceedings," it read.

She said that opinion was based on Ms Edwards' mention of the divorce and the delayed reporting.

"When she didn't bring the children, I didn't think it was as pressing as she'd made out," the 18-year veteran said.

Under questioning, she agreed there may have been a good reason for the delay and that the delay and court proceedings didn't mean the allegations were untrue.

The inquest resumes on Thursday.

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Australian Associated Press