Accused gunman Dezi Freeman is probably still alive as the police manhunt for him enters day 21, a criminologist and forensic expert says.

Xanthe Mallet was speaking with Today this morning after Victoria Police said the search for Freeman in the state’s high country had been the biggest tactical operation in Australian policing history.

“My sense … would be that he’s possibly still on the run. He may have people assisting him,” she said.

Freeman allegedly shot dead police officers Neal Thompson, 59, and Vadim De Waart-Hottart, 34, and injured a third last month, sparking a huge manhunt.

Last Friday, specialist tactical police from across Australia and a contingent of New Zealand officers launched an extensive search in rugged terrain around the town of the Porepunkah, where Freeman had been living.

But police conceded they are no closer to finding Freeman as he remains at large for a third week.

Mallett says Freeman could be dead or bunkered down, but he could also have travelled some distance from Porepunkah, forcing police to widen the search zone.

Police have characterised the accused gunman as a skilled outdoorsman who has extensive knowledge of the local area.

Mallett says she thinks police have been overwhelmed by more than 1000 calls from the public reporting possible leads, but they hold the key to finding Freeman.

“They need those calls. They need the public’s help because that I think is going to be one of the key ways we’re going to find him.

“Somebody will come across him at some point.”