The tight-knit community connected to suspected killer Michael Burdon could be withholding crucial information about the whereabouts of his wife, South Australian police have revealed.
Detectives working on the mysterious case have now turned their attention to the two days after 23-year-old Tanja Ebert disappeared.
Ms Ebert, a mother of two, was reported missing on August 10 last year - two days after she was last seen.
Mr Burdon, 41, fatally shot himself at their remote Manna Hill sheep station less than a week later, leaving police with no clue as to where Ms Ebert's remains might be.
But, one year on, police say people known to Mr Burdon could be withholding information that would uncover his secret.
"We suspect Michael has committed the murder of his wife, we don't believe anyone else was involved in that," Detective Inspector Billy Thompson told reporters on Monday.
"Whether other people chose to assist Michael after the murder is a question that we need answers to."
Police have announced a $200,000 reward for anyone with information that could lead to the recovery of the woman's body.
Officers are now focussed on tracing Mr Burdon's actions between the last sighting of Ms Ebert and the time she was reported missing.
"We've conducted some inquiries in relation to Michael's movements from (Tuesday) the eighth of August until the time of the report of Tanja's disappearance," Det Insp Thompson said.
"There's a period on the Wednesday of a number of hours that we can't account for, there's also a period on the ninth that we can't account for as well.
"We suspect someone does know what he was doing during those two days."
The couple and their children had spent August 8 in Adelaide visiting the SA Museum, with the last confirmed sighting of Ms Ebert in the city that afternoon.
While Mr Burdon initially told police his wife, carrying $2000 in cash but no phone or passport, got out of the car in the town of Roseworthy, they now believe she returned to the property at Manna Hill.
The sprawling 410 square-kilometre station has been searched three times, but nothing of interest has been found.
Det Insp Thompson urged anyone with information to come forward for the sake of the couple's two young children, who are now in the care of Mr Burdon's family.
"People might be reluctant, out of respect for the Burdon family, to come forward and talk to us," he said.
"It's obviously going to be terrible as these kids grow up and want to know what happened to mum and not having any answers."
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