Criminal experts believe a “third party” is involved with the disappearance of Gus Lamont after police were forced to scale back the search this week for the missing 4-year-old in remote South Australia.

Augustus “Gus” Lamont was last seen by his grandmother playing in the sand in a Minions T-shirt at his family sheep station near the town of Yunta about 5pm on September 27. When she went to call him inside about half an hour later, the preschooler was nowhere to be seen.

Police were forced to scale back the search on Tuesday after a 10-day effort involving helicopters, drones and Aboriginal trackers failed to yield any clues into the child’s disappearance.

Speaking to news.com.au, criminologist Xanthe Mallett said all signs now pointed to a third-party involvement.

“Given he’s so young, it’s very unlikely that he would have run away. That’s more a teenager kind of thing,” she said.

“The scale of the search and how detailed it was, and the drones and everything else, it does feel at this stage, sadly, that if they haven’t found something that it’s likely to be third-party involvement.”

Little was found in the 10-day search except for a “small boot print” near a dam.

However, the footprint was later ruled out with police saying it was not related to the search.

Mallett said given the “remote” nature of the area near Oak Park Station, the lack of evidence found in the search also points to a third party.

“When they were looking for [alleged police killer] Dezi Freeman, that was a really hard environment to search by plane or drone because it’s such dense bushland, whereas this isn’t that kind of scenario,” she said.

“If he were wandering or had fallen, then the technology and the search strategies they’ve applied should have located him.

“The fact they’ve scaled back means that they feel that they have searched well enough to do that. So, it does feel sadly like that there’s probably somebody else involved.”

Next stage of investigation

Police believe Gus was living at the remote homestead with his mother Jess, his 1-year-old brother Ronnie and his grandparents.

Police are expected to be shifting their focus to a possible third party in the case of missing boy Gus Lamont. Photo / NewsWire/Dean Martin

It is believed Gus’ father Joshua lives in Blalie North near Jamestown, about 100km west of the homestead.

None of Gus’ family members is accused of any wrongdoing or involvement in his disappearance.

Speaking generally about missing children’s cases, Mallett said police are likely to start looking into those “physically present” at the time of Gus’ disappearance.

“Especially with young children, they will look at those family dynamics,” she said.

Phone tower pings

Mallett also said one major component of the case, which will assist police, is the lack of phone towers in the remote area.

In the case of Cleo Smith, who was taken from a campsite in Western Australia, a single ping to a phone tower, which was only built in 2018, helped lead police to the phone of her kidnapper, Terence Darrell Kelly.

“There won’t [have been] that many people in that area,” Mallett said.

“So those people whose phones do ping, [police will] be able to track down and speak to.”

William Tyrrell lead detective weighs in

Former homicide squad detective Gary Jubelin is also of the opinion that another person is involved in the Gus Lamont case.

The investigation is now being managed by the missing persons section, with ongoing lines of inquiry. Photo / Supplied / SA Police

Jubelin said the fact police were looking at third-person intervention was a lesson learnt from the William Tyrrell investigation, in which he said the “whole focus was on finding the little boy lost”.

“Children disappearing at that age is a rare event,” he told Nine’s Today show on Wednesday.

“What police would be looking for is, has the disappearance been the result of wandering off, misadventure and getting lost, or is there some form of intervention involved in his disappearance?

“What I’m seeing now and what I’m reading between the lines of what South Australian Police [are doing], they’re looking at other possibilities that there was perhaps intervention. So it’s difficult for the families involved and even for the police.”

On Tuesday, Deputy Commissioner Linda Williams revealed the case had been moved to the missing persons section.

“The investigation is now being managed by missing persons section, which is part of Major Crime Investigation Branch, and that’s where all long-term cases such as this are managed and investigated,” Williams said.

“We will never give up hope of finding Gus.

“There are further lines of inquiry being undertaken and the family have continued to co-operate fully with police.”

Police earlier deployed a special drone in the search, with Williams confirming the “significant aerial search” involved a special drone with infra-red capabilities.

“The results of that drone analysis are still being analysed. We hope to have those results in the coming weeks.”

In a statement, SA Police said they were continuing to look at “all options”.