Police have secretive ways to communicate with an accused cop-killer if he bows to their unrelenting surrender pleas, as the cost of the massive air and land tallies up.
Dezi Freeman remains at large in Victoria's high country after allegedly gunning down Senior Constable Vadim De Waart-Hottart, 35, and Leading Senior Constable Neal Thompson, 59, on August 26.
There has not been any confirmed sightings of the 56-year-old since he fled into dense bushland near a Porepunkah property where officers were serving a search warrant.
Police believe he is still alive and people possibly know where he is hiding.
The force and his wife, who was present during the shootings, have publicly called for Freeman to give himself up through a surrender plan.
"Your destiny is in your hands," Victoria Police Chief Commissioner Mike Bush said in the nearby area of Ovens yesterday.
Such a plan involved police giving a wanted person clear and simple instructions, former hostage negotiator turned criminologist Vincent Hurley said.
"[It's] as if you're talking to a 10-year-old," the lecturer at Sydney's Macquarie University told AAP.
"When you're talking to someone who has been out in the environment like that, who has been worn down over time and could be really hungry, fatigued and mentally exhausted ... you're talking in short, easy to understand, concise language."
Every question should be followed up with confirmation of comprehension and a warning any behaviour outside of it may be cause to shoot, the ex-NSW Police detective superintendent said.
Hurley said police could make contact with Freeman if he didn't have a mobile phone or service was patchy, including through a loudspeaker.
There were also other ways to communicate but he wouldn't go into detail, saying crime figures would be watching the unfolding search in the hope of learning operational strategies.
"I know for a fact, as a negotiator for eight years, underworld figures and organised crime syndicates – they watch this and they take notes and learn," he said.
More than 100 properties in the Alpine area, about 300km northeast of Melbourne, have been searched.
The Australian Defence Force has joined the operation at the request of Victoria Police, deploying a planning specialist and air surveillance assets to aid the more than 400 personnel on the ground.
Bush has pledged to share the "real cost" of the massive manhunt with taxpayers at some point.
Hurley suspected Freeman, who has shared views consistent with the sovereign citizen movement and is considered to be an experienced bushman, will have stashed food, water, clothing, ammunition and firearms in a fairly dry location.
That's more likely to be in a cave or rock shelf, rather than a mineshaft, to make sure the supplies are out of the elements, he said.
Bush said police had considered every investigative option to find Freeman, including offering a financial reward for information leading to his capture.
Hurley cautioned against going down that path, noting anyone with information on Freeman's whereabouts likely shared his sovereign citizen beliefs and it could prompt fake leads that would have to be followed up.
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