Victoria Police is fighting to keep details secret of its new "evolved" car pursuit policy ahead of an inquest into the Bourke Street massacre.
Police cars had chased James Gargasoulas before he drove down Melbourne's Bourke Street Mall, killing six people and injuring dozens of others.
On Wednesday, a lawyer for the chief commissioner argued Gargasoulas knew about the police no-pursuit policy at the time, so details of the force's new policy should remain confidential in the interests of public safety.
"When it became publicly known that police would back off from pursuing certain drivers ... that resulted in persons adopting that form of behaviour," Ian Freckelton QC argued before coroner Jacqui Hawkins.
"The offender ... knew where the lines were, what he could do, and what he could get away with.
"That's the risk of the public knowing where the lines are."
He said police pursuit policies had "evolved" and changed "significantly" since the January 2017 massacre.
Dr Freckelton said police weren't seeking to suppress details of the pursuit policy at the time, which needed to be "fully canvassed" during the inquest.
The police also want to keep secret a critical incident review done in the immediate aftermath of the tragedy, aspects of the assistant commissioner's report and the names of special operations group officers.
But lawyer Sue McNicol QC, who is acting for the families of the deceased, argued against suppressing documents from publication.
"The reports are inextricably intertwined with the issues to be ventilated," she said.
"You cannot unscramble this egg."
She added it wasn't clear whether Gargasoulas knew about the force's pursuit policy because of media reports or his own "extensive history" of dangerous driving.
Aine Magee QC, also acting for the victims' families, argued the inquest should be broadened to explore "whether there were opportunities that were lost" in preventing the massacre.
Ms Magee said failures in emergency services responses also needed to be examined, after 10-year-old victim Tahlia Hakin's father was led to believe his daughter was still alive, but was prevented from going to her.
"He firmly believed he may have been able to save his daughter's life," she said.
The one-month inquest, with 46 witnesses, will run November 18 until December 20.
It will also investigate the justice system's treatment of Gargasoulas, including an out-of-sessions bail hearing that released him from custody just days before his deadly rampage.
However, the inquest will not consider the correctness of the bail justice's decision.
The murderer, who suffers paranoid schizophrenia, was handed a life sentence in February and will not be released for a minimum of 46 years.
A further directions hearing will be held on August 23, during which Ms Hawkins will deliver her ruling on the suppression order applications and the families' request to broaden the inquest's scope.