Murray, whose four-year-old grandson vanished from her homestead in South Australia's Far North in September 2025, was fined $10,500 in Adelaide Magistrates Court on Friday.
She had pleaded guilty to possessing a silencer for a .22 rifle after the court heard the 75-year-old had a previous conviction involving the theft of unsecured firearms by a fugitive.
Defence lawyer Andy Ey told magistrate Roderick Jensen that he would "address the elephant in the room".
"It's been an extremely difficult time for my client. A grandchild went missing on the property late last year," he said.
"This has been a very, very difficult time for the family, trying to get through as best they can."
Gus Lamont was last seen by one of his grandmothers playing at the family homestead at Oak Park Station on September 27.
On February 5, police declared the boy's disappearance a major crime and said someone living at the remote station was a suspect in the case and his likely death.
Four support letters were submitted to the court, including from Murray's wife Shannon, "that clearly talk to her otherwise exemplary character", Mr Ey said.
He said Shannon Murray was simply a close friend and business partner since his client's 2009 gender reassignment.
Murray had lived most of her life at Yunta and had gone to St Peter's College where she was head prefect, Mr Ey told the court.
She met her wife at school, briefly studied law and returned to the country to be a stockman and drover.
The couple had run Oak Park for almost 50 years.
Murray was a licensed builder 25 years ago, had been a marriage celebrant and also a long-time Justice of the Peace, Mr Ey said.
Prosecutor Tania Stevens told the court police had executed a search warrant at Oak Park on January 15 over an "unrelated matter".
Inside a passcode-protected strongroom, they located the silencer and several firearms, including one that was modified to fit the silencer.
Murray had a 2010 conviction for falling to securely store firearms, Ms Stevens said.
That offence arose as a result of a fugitive trespassing on the defendant's property and stealing an unsecured firearm.
"That person then went on to commit serious offending with the firearm before taking his own life," she said.
Mr Ey clarified that two non-working firearms were taken, while a third one was taken from Murray's auntie's property later that day, "which is the firearm that the trespasser used to take his own life".
"That was an extremely traumatic incident for the entire family, with my client's auntie being held hostage," he said.
Police had seized the stolen firearms and silencer and later returned them to Murray.
At the time, it was not an offence to possess the silencer, but that changed when the Firearms Act was amended in 2017.
Mr Ey urged the magistrate to reject the prosecutor's call for a jail term for the offence, which carried a maximum penalty of $75,000 or up to 10 years in prison.
"This isn't some James Bond movie where you've had ... an assassin walking around the corners taking out targets with little more than a whisper of a gun," he said.
Mr Jensen imposed a $10,500 fine and disqualified Murray from holding a firearms licence for five years.
Gus' disappearance sparked intensive searches spanning almost 500 sq km.
Police confirmed his grandmothers, his mother and his younger brother were at the property at the time he disappeared but emphasised his parents were not suspects.
Detectives also said a family member living at the property had withdrawn co-operation from police.
Both grandparents previously released a statement saying the family had co-operated with the investigation and wanted nothing more than to reunite Gus with his parents.
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