Victoria Police's outdated IT system was one reason officers were unaware of outstanding arrest warrants when visiting Greg Anderson’s address in Chelsea Heights over an assault on January 27.
Chief Commissioner Ken Lay said there was a "gap" when unexecuted warrants returned to the responsible officer, and the warrants were not visible to wider police for two weeks.
"If police would’ve gone to that address a day later, those warrants would have been visible,’’ Mr Lay said.
"There were five warrants of apprehension in existence ... our members in attendance would not have been aware of those warrants because of shortcomings in our IT system.’’
Mr Lay's comments came as Victoria's Children's Commissioner Bernie Geary announced an inquiry into the death of 11-year-old Luke Batty, killed by Anderson, his father, on Wednesday.
Mr Geary said the review would be conducted to determine whether the "system" had failed Anderson and, as a consequence, his son and estranged partner.
Mr Lay said the police IT shortcomings were only one factor in a ‘‘complex’’ set of circumstances.
“This is not me blaming an IT system for the death of a young boy. It is one part of a very complex issue for us,’’ he said.
Mr Lay said various reports had highlighted the force’s antiquated IT system, which had been neglected for 15 years.
He said the state government made a considerable investment to improve it a year ago but it still required an overhaul.
Mr Lay said he would not usually speak publicly about such a significant police issue so early in an investigation, but the groundswell of public interest and his personal focus on family violence had prompted him to talk about the ‘‘tragic incident’’.
He said there were a number of questions that needed to be asked, including whether the judicial system provides enough protection for victims of family violence, and whether police should have been better equipped to prevent Luke’s death.
‘‘We can get changes through tragedy,’’ he said.
‘‘We know there are thousands of young Lukes out there, we know there are thousands of Rosies out there. We need to invest in this.’’
Mr Lay said earlier that Anderson, 54, should have been in jail at the time of his son's murder.
Mr Lay told Fairfax Radio the January incident involving Anderson was unrelated to domestic issues involving his former partner Rosie and his son Luke but that he was aware there had been "some suggestion of threats of violence" from Anderson to his family.
The outstanding warrants were issued in January this year for repeated failure by Anderson – who lived between a caravan and a car in squalid conditions in Chelsea Heights – to attend court dates.
He said that it was ‘‘easy to say in hindsight’’ that Anderson should have been in jail. But it was ‘‘too soon’’ to judge the actions of police without a full investigation.
It has been revealed Greg Anderson – shot dead by police after the brutal assault on his son – had a long history of mental illness and was known to the Department of Human Services.
"Quite clearly, in this case, the family had a connection to the department," Children's Commissioner Mr Geary said. "And the death of Luke, with a connection to the department and its services, requires a pretty fulsome review to determine whether there was the proper services and assistance available, to see if all the links in the chain worked correctly."
Mr Geary cautioned against assumptions that mental illness was a common root cause of "insidious family violence in the community".
"I would urge the people of Melbourne to consider that not all people with mental illness are violent, in fact only a small percentage are violent. And ... only a small percentage of family violence offenders have a history of mental illness. Mostly these men are cowards before anything else."
The inquiry will take place over the next few weeks, Mr Geary said, and would involve talking to Luke's mother Rosie Batty, members of the Tyabb community and mental health workers who may have dealt with Anderson.
In an emotional statement to the media less than 24 hours after watching her beloved son die, Ms Batty said her estranged partner was a man who loved his son but had suffered from an undiagnosed mental illness for two decades.
She says Luke loved his father and "felt pain" because he knew he was struggling.
"He was a little boy in a growing body that felt pain and sadness and fear for his mum, and he always believed he would be safe with his dad," she said.
"[I told him] 'you'll always love your dad. You won't always like what they do or say, but you'll always love your dad, and he'll always love you'."
Ms Batty says she had known Anderson for 20 years, and over that time his mental health deteriorated.
"[He went] from someone who brushed off losing a job to someone that was unemployable," she said.
"He was in a homelessness situation for many years. His life was failing. Everything was becoming worse in his life and Luke was the only bright light in his life."
Anderson had repeatedly been offered help, she said, but he failed to accept it, instead choosing to "believe he was OK".
She had permitted Luke to have contact with his father as there were no signs he would ever hurt their child.
"You're dealing with someone who's always had problems, and they start out small and over the years they get bigger, but he's still the father," she said.
"He loved his son. Everyone that's involved with children would know that whatever action they take is not because they don't love them."
Mr Geary said Luke's death held the same tragic resonance as the Robert Farquharson and Arthur Freeman cases (the former convicted of murdering his three sons on Fathers Day in 2005 by driving them into a dam and the latter convicted of murdering his five-year-old daughter by throwing her off the West Gate Bridge) and had sent the same tremors through the community.
"I would hope that all Victorians would take their lead in dealing with the news of such a tragedy from this incredibly compassionate mother who has been so brave and strong in speaking of her son and former partner."
Prime Minister Tony Abbott described Luke Batty’s death as an ‘‘unspeakable tragedy’’.
‘‘Just horrific, horrific beyond words,’’ Mr Abbott told Fairfax Radio on Friday.
But the Prime Minister said that, while he did not want to minimise the 11-year-old’s death, he did not believe the federal government needed to take any specific action.
‘‘We’re always asking ourselves the question, ‘what more can usefully be done?’ ’’ he said.
‘‘[But] without trying to slide out of responsibility ... there are tragedies that happen in life.
‘‘I'm not sure that every tragedy requires a change of policy, or every tragedy requires a new program.’’