Four police officers missed the opportunity to arrest Greg Anderson two weeks before he killed his son Luke Batty because of an incomplete police data system.
Police from Chelsea took the unusual step of sending four officers to Anderson's address on January 27 to serve an intervention order taken out by a housemate, because they knew of his violent reputation, an inquest into Luke's death heard.
The officers conducted the relevant background check on Anderson but found no record of outstanding warrants, a lawyer acting for Luke's mother Rosie Batty told the inquest.
"They knew of Anderson's reputation so sent four police officers out to serve the intervention order," Rachel Doyle SC said on Thursday.
"They conducted the relevant inquiries and found no record.
"Hastings (police) has been furiously looking for him and Senior Constable Lynch at Chelsea finds him but wasn't aware of outstanding warrants."
Police Chief Commissioner Ken Lay in February said the IT system failure was one piece of a complicated case and there was no way of knowing if Anderson would have been held in custody or immediately bailed even if he had been arrested before the murder.
Anderson killed 11-year-old Luke by hitting him with a cricket bat and attacking him with a knife as they played in the nets after cricket training at Tyabb oval on February 12.
The Victorian Coroners Court earlier heard that early in May 2013 police at Hastings had received emails about Anderson from other police, including one that said "going postal would definitely apply to this bloke".
Another email said Anderson was avoiding police and was belligerent.
It provided several possible contacts for Anderson, who had no fixed address at the time, including a phone number for his solicitor.
Senior Constable Kate Anderson of Hastings police station told the inquest this information was not used to contact Anderson.
Anderson, 54, was shot dead by police after he lunged at emergency service workers called to the oval when he killed his son.
Ms Batty told the inquest that finding the strength to stand up to her violent ex-partner ultimately got her nowhere and holding him accountable brought new levels of fear and anxiety.
"When he threatened to kill me and chop off my foot, that was the line in the sand," she said on her third day of evidence.
"And look where it got me.
"When you make the stand and when you decide to, you are alone and you don't know what you're facing and there is an underlying fear and terror because you don't know what is going to happen."
The inquest also heard the Department of Human Services closed its child protection file on Luke in October 2013, four months before he was murdered.
