Luke Batty's killer father wouldn't have gone to jail even if he had been arrested on outstanding warrants before the murder, the boy's mother says.
Greg Anderson was wanted on five warrants when he killed the 11-year-old boy last week after Tyabb cricket training on the Mornington Peninsula.
Police have blamed the force's ageing IT system for failing to alert officers the warrants existed when the 54-year-old was questioned about an assault three weeks before the killing.
But Luke's mother, Rosie Batty, says those offences weren't severe enough to keep her ex-partner in custody.
"The truth of the matter is, Greg's conduct would not have put him in prison," she told Triple M on Monday.
Ms Batty said it wasn't right to blame cracks or glitches in the system for her son's death either but the answer involves seeing men collectively take a stand against domestic violence.
"It starts with men. Don't blame systems," she said.
"It took me years to understand that violence isn't just about hitting somebody. There are many forms of abuse."
Ms Batty tried to surround Luke with positive male role models when her ex-partner became violent.
She said she found support in former AFL star Matt Rendell, who became "Big Matt" in Luke's life.
"He adored Matthew," she said.
Luke's father was shot dead by police after the killing.
Ms Batty said he had been suffering from paranoia for years but there's no record of him having contacted a mental health service.
Mental Health Minister Mary Wooldridge said it's common for the mentally ill to first come into contact with services through police or the courts but it's difficult to force someone into treatment.
She said it was feasible to track those on intervention orders with ankle bracelets, just as sex offenders are currently tracked.
"The question is how far you go," she said.
Multiple investigations are underway into Luke's death.
Premier Denis Napthine said these inquiries will help agencies reduce the risk of a similar tragedy happening again.
