Josie Murray's bombshell interview over her missing grandson Gus Lamont has ignited fresh questions over the seemingly stalled nine-month investigation.

The four-year-old vanished on September 27, from his grandparents' remote sheep station in the South Australian outback near Yunta, 300km north of Adelaide.

Police initially believed he had wandered off while playing out the front of Josie and Shannon Murray's Oak Park homestead, where Gus was living with his mother, Jessica, and baby brother, Ronnie. 

However, in February, police declared his disappearance a major crime, and said they believed someone had killed him, either accidentally or on purpose - and that one of his grandparents was a suspect after both allegedly withdrew their cooperation.  

On Sunday, Josie, 75, was interviewed by Channel Seven's Spotlight, and confirmed she was the main suspect in the investigation.

She told the program police believe she may not have hurt the four-year-old, but possibly buried him, which she vehemently denied. 

No arrests have been made and no charges have been laid. 

But the revelation that Josie is now the main suspect raises fresh questions about the sequence of events on the day Gus vanished.

The child was reported to be in the care of Shannon when he was last seen playing outside at 5pm. At the time, Josie was said to be several kilometres away with Jessica, tending sheep in a distant paddock.

On Sunday night, Josie said she and Jessica returned to the homestead around 5.30pm to find him missing. 

She revealed she and Jessica searched for Gus on foot and on motorbikes, maintaining contact on CB radio and rarely out of each other's sight.

Later, after nightfall, she and Shannon scoured the scrub in the dark on their motorised buggy.

In February, when announcing they had a suspect, police said they had identified 'a number of inconsistencies and discrepancies' in the family's timeline of events. 

Despite being repeatedly asked, they have never revealed what those inconsistencies were. 

They also ruled out that he had wandered off or been abducted due to lack of evidence - something Josie believes was a mistake on the part of investigators.

Instead, Josie insisted that Gus was abducted - and that she believes the boy is still alive. 

'We haven't got a body,' she said. 'We haven't got a live body. We haven't got a dead body.

'We have no idea quite where he is, but we feel that yes, he has been taken.'

She said she told a local police officer that she had noticed 'suspicious' signs near an uncompleted cellar, which the family referred to as 'the bomb shelter'.

According to Josie, a rusted bedstead and a weather station had been moved, and there were strange tyre tracks nearby. 

Josie described her frustration that these potential leads in the early days of the investigation were dismissed.

She also feared some crucial evidence may have been destroyed when hundreds of people - including police, searchers and media - descended on the property.

She said police appeared to believe that Gus might have died by accident, and that Josie buried the body, which she described as 'ludicrous'. 

'We absolutely know we're innocent,' she said.

'We know that we couldn't and didn't do anything and the hard part obviously is to convince other people of that. 

'There's no way of completely convincing people.'

Seven crime reporter Hannah Foord had been trying to secure an interview with Josie since Gus went missing, and on June 12, the grandmother contacted her and said she would speak - but it was now, or never. 

Josie has retained criminal lawyer Andrew Ey, of Mangan Ey and Associates. It is not known how tightly he controlled the interview. 

Given Josie appeared to believe from the start that an abduction could have occurred, it raises questions over why the family waited six days to release a picture of Gus. 

In suspected abductions, it is customary to release an image of the victim in the hope a member of the public will spot them.

Daily Mail approached SAPOL two days into the search on September 29 asking for a picture of the missing child.

Police responded: 'At the request of the family, we are not releasing a photo at this time.'

According to police and to Josie, Shannon Murray was the last to see Gus alive. 

She has never publicly spoken, aside from occasional statements through her own lawyer Casey Isaacs. 

She insisted she supports Josie and just wants Gus home.

When Josie appeared at Adelaide Magistrates' Court on June 12 facing gun charges unrelated to Gus's disappearance, a letter of support from Shannon revealed the pair have not been living as a married couple since Josie's gender transition from male to female in 2009. 

She said they are simply close friends and business partners. 

The pair are regularly seen in each other's company in Jamestown and Peterborough, villages near Oak Park. However, Shannon was not by Josie's side at two crucial moments - when she appeared in court earlier this month, and when she gave a tearful interview to Spotlight. 

It is not known why she has chosen not to appear publicly. 

Instead, Josie's only public supporter appears to be her longtime friend, well-known South Australian equine vet Bill Harbison - brother of former Adelaide Lord Mayor Michael Harbison. He was alongside Josie at court as she faced a media scrum. 

With no sign of Shannon, Bill was extensively interviewed by Spotlight and spoke critically of police. 

He described the police attention on his friend as 'tunnel visioned' and 'vindictive', and even suggested Josie had been subject to 'discrimination... targeting her because of her transgender situation – and they were mortally offended that I should say it'.

On Monday afternoon, SA Deputy Police Commissioner Linda Williams said the suggestion was 'nonsense'. 

'When we conduct an investigation, we always do it impartially. I am very proud of the professionalism shown by our officers,' she said. 

While Josie was focused on the abduction possibility, Bill returned to a long-discounted theory that Gus had been picked up by a wedge-tailed eagle. 

Josie's interview suggested cracks in the relationship with her only daughter Jessica, who the Daily Mail understands fled Oak Park with her younger son Ronnie after police declared a major crime. 

'Jess is not so prone to talk about [the situation], particularly to me,' Josie said.

Meanwhile, during the interview, Gus' father, Joshua, barely rated a mention.

Daily Mail understands he fell out with Josie prior to Gus's disappearance and was no longer welcome at Oak Park. 

Sources said he attended the property just once to help with the search, but left after an altercation with Josie. 

Josie did not touch on this alleged feud within the family, and Josh, who has been approached for comment multiple times, is refusing to share his side of the story.

Going by Josie's account, it appeared Gus led an independent life on the farm, and was known to go wandering off.

It was revealed he had previously 'gone for a walk' while under the care of Shannon, but that Josie had found him.

He would often be seen entertaining himself around the property while his grandparents and mother worked. 

'He was quite happy to go and play on his own...You'd often hear him down at the shed, you know, he's got a fixation on opening and closing the Hi-Lux doors at one stage and you'd hear this, 'bang bang bang bang'.

'We just said well if that's what he wants to do, he's not going to hurt anything terribly much.

'He was fairly quiet. He would get upset occasionally, like all kids, that's normal,' she said.

'He was happy, perhaps not more than you'd expect but he was happy most of the time.'

Josie described his blonde, curly hair as his 'crowning glory' but urged Australians not to focus too much on it if they are looking for the boy, seeming to suggest an abductor would have changed his appearance.

The public now awaits investigators' response to Josie's interview claims.

Taskforce Horizon is expected to examine the interview closely. However, SAPOL declined to participate on-camera for the Spotlight special. 

Instead, they responded with a statement, via a spokesperson.

'Sadly, despite 11 individual, large-scale searches of Oak Park Station, no evidence relating to Gus Lamont's disappearance has been located.

'Taskforce Horizon has and will continue to investigate all information, including information provided by Gus' family that could assist in identifying what has happened to Gus.

'As the investigation is ongoing, it is not appropriate for SA Police to discuss specific aspects of the investigation that could compromise future court proceedings.'