The Jetstar pilot charged with murdering two elderly campers will appear in court Friday morning after an 'exhaustive and complex criminal investigation', but one of Victoria's top cops says a vital piece of evidence is still missing.
A trailer being towed by an off-road vehicle captured on CCTV the night secret lovers Russell Hill, 74, and Carol Clay, 73, vanished in the Wonnangatta Valley, is yet to be accounted for.
Police seized a Nissan Patrol belonging to Gregory Lynn, 55, on Monday when Special Operations Group officers dramatically arrested the Caroline Springs man after tracking his movements and flying into remote bushland by helicopter.
A subsequent search of his property did not uncover a trailer which police believe could be the final piece of the puzzle, as forensic crews prepare to search for the pair's remains at a second 'crime scene' discovered on Thursday morning in the remote Great Alpine region.
In the hunt for human bones, specialist teams will also deploy ground-penetrating radar at Lynn's two storey home in Melbourne's West - the same technology being used in the search for missing NSW child William Tyrrell.
Gregory Lynn, 55, (pictured) was charged with the murder of secret lovers Russell Hill, 74, and Carol Clay, 73, as police begin the exhaustive search for their bodies
Police have been unable to account for the trailer (pictured) being towed in the CCTV footage the night the couple vanished near a remote camping spot
Russell Hill (pictured, left) and Carol Clay (right) are alleged by police to have been murdered during a camping trip in March 2020
Assistant Victoria Police Commissioner Bob Hill said investigators are keen to speak to anyone who may have purchased a rusty silver or blue 7x5 ft trailer with off-road wheels between March 20 to July 2020.
'We believe the trailer was sold on Gumtree,' he said.
Earlier this month, police made a public appeal for a blue late 90s Nissan Patrol - the same make and model police seized from Lynn during his arrest in Licola, about 100km south of the where the couple went missing.
But Lynn's vehicle was coloured beige, not blue.
Assistant Commissioner Hill said he's 'proud' of police efforts during the 20-month long police probe, but added the 'long haul' investigation is 'far from over' as the focus now turns to uncovering the couple's remains.
Keen camper and dad Gregory Lynn, 55, (pictured) has been in custody since Monday and will face court on Friday morning
An Australian flag sits proudly in the top window of the Lynn's property in Caroline Springs (pictured)
For 20 months police have been investigating what happened to the two missing campers
'This morning detectives identified a crime scene within the Great Alpine area and forensic specialists will commence searching at that location over the coming days,' Assistant Commissioner Hill said.
'We have located a specific area and we will establish a search parameter.
'Police are hopeful we will be able to locate the deceased in order to find closure for the families.'
While the search is taking place in remote bushland, forensic specialists will also be scouring Lynn's two-storey home in Melbourne's west.
Ground-penetrating radar which can uncover anomalies deep within the earth or even concrete structures will be brought to assist the evidence gathering operation.
Police put out a public appeal for this 4WD (pictured in a police sketch) with roof racks, side steps, off-road tyres and a bulbar. The box trailer is 'fairly standard' but has been fitted with 'off-road wheels', detectives say
The beige off-roader belonging to