It would be really helpful if police would publish a timeline of when they made various conclusions.
For instance, police obtained the mobile phone tower records - I have not seen when they did this - and discovered when Mr Hill's phone "pinged" the Hotham Heights phone tower about 9.47am. A Nissan Patrol, later found to belong to Mr Lynn - police have to establish he was driving, is photographed by traffic cameras on the Great Alpine Road at Buckland’s Gap, about 9.48am. The tower is described as being "near by". The vehicle is towing a box trailer. I have not seen when police obtained the photographs from the traffic camera. My understanding is that a phone tower can provide the general direction, from the tower, the phone is located when it "pings" the tower. So, it may be possible to suggest a degree of co-location; that is to say, the phone was in or near the vehicle.
When police linked the two records, that is, the time the phone was communicating with the tower and Mr Lynn's vehicle was photographed, did they know that Mr Hill was dead - and if so how?; or is that something they concluded from other evidence and then, applied that belief to the information about the phone and the vehicle?
It seems to me that police are, quite rightly, alleging that at the time Mr Hill's phone communicated with the cell tower and Mr Lynn's vehicle was photographed, but they cannot use this information as proof that Mr Hill was dead at the time the vehicle was photographed. After all, Mr Hill's phone could have been tossed in the trailer, as an elaborate ruse to blame Mr Lynn. That is the type of conjecture the prosecution will face.
In short, if police allege Mr Hill was dead at the time his phone communicated with the phone tower, how have they reached that conclusion?
I suspect - and this is only conjecture on my part - Police noticed the correlation of Mr Hill's phone pinging the tower and the Mr Lynn's vehicle being in the vicinity - and quite rightly worked to find out if this correlation was connected with Mr Hill and Ms Clay's disappearance. The question would then be: Why was Mr Hill's phone in the vicinity of the cell tower, some kilometers from his camp site?
As a final observation, the police have not said what led them to conclude by mid 2020 that Mr Hill and Ms Clay were dead and had met with foul play at the hands of a third person. Their surveillance of Mr Lynne began in December, 2020.
I think that kind of police work: determining whether RH had been kidnapped or had voluntarily gotten a ride, had his phone stolen or was it there by accident, was he alive or dead: that's a long process of elimination. As Sherlock Holmes said, 'When you have eliminated the impossible, whatever remains, however improbable, must be the truth.'
IMO, fairly early on they narrowed down the ping and the vehicle-video connection. Immediately, IMO, they would have been suspicious because GL hadn't come forward voluntarily, to give a story, perhaps such as early poster Ramjet offered, that he'd rushed them to hospital and left them in Emergency...
For an example of eliminating the impossible: the possibility that they ran off together (leaving their truck and ID behind), and started a new life, eventually becomes impossible: given their characters, health, circumstances, previous behaviour, lack of any trace or evidence of planning it, and the passage of a long period of time and widespread publicity that everyone is upset/looking for them...if LE were to continue to keep that open as a possibility, they would be deservedly fired and replaced with more responsible people who took their job seriously.
Similarly, they ruled out the involvement of every other person who had been at the campground that night, and so on, and so on, any other possibility is eliminated.
Plus, their suspicions are reaffirmed by incidents such a GL painting his truck, etc.
Altho they were satified, I think they wanted the smoking gun: forensic evidence. They invested enormous resources into listened to him for months, if they had found solid proof, they wouldn't have wasted so much manpower on that. But they couldn't wait any longer, and fortunately, appear to have gotten the evidence they needed, after arrest.
What I can't get over is, why GL left RH's phone on? Thank goodness he made that mistake.