Coroner Michael Holmes found Christopher Phillip Jeffery, 58, and David Anthony Hicks, 41, were killed instantly in the June 14 crash in 2016, 15km north of Uralla.

He made one recommendation after a dog uncovered some of the remains in the police holding yard, about a month after the collision.

The inquest in Armidale Coroner’s Court heard a nearby resident’s dog got in through a hole in the fence and was found with “a human foot within a work boot and sock” in its mouth.

“The discovery of Mr Jeffery's remains within the wreckage, and the manner in which that discovery came about, is a shocking event,” Mr Holmes said in his findings.

“It has caused considerable and understandable distress to the Jeffery family. The preservation of exhibits and the recovery and sensitive handling of remains a matter of concern for police, the Coroner's Court and the wider community.”

He expressed his sympathy to the Jeffery family for their ordeal because “it became clear to all involved”, “that the Guyra holding yard's fencing was inadequate”.

“It had holes in the fence that permitted animals such as the nearby resident's dog to enter the yard,” he said.

“The fencing at the yard has since been replaced.”

He has recommended the NSW Police Commissioner conduct an audit and review the operating arrangements at holding yards for police to strengthen security and preserve evidence and exhibits, including any wreckage or vehicle. 

The inquest heard experts “agreed that there was no possibility of Mr Jeffery himself avoiding the collision at this point”, after the deviation occurred about “1.5 to 2 seconds prior to impact”, on Thunderbolts Way at Scrubby Gully.

Mr Jeffery was behind the wheel of a Kenworth prime mover carrying two trailers of grain, while Mr Hicks was driving a Volvo prime mover with 26 head of cattle on board.

The inquest heard Mr Hicks’ Volvo “underwent a significant change in direction” into the path of Mr Jeffery’s truck.

“Regrettably, despite the very best efforts of the investigators and experts involved, it is not possible to determine the exact cause of Mr Hicks' sudden movement into Mr Jeffery's lane,” Mr Holmes said.

“Numerous possibilities have been examined, some of which can be excluded and others, whilst unlikely, are not matters that can be definitely excluded in the circumstances.”

Mr Holmes said speed was not a factor, the collision took place on a straight stretch of road, and the volvo’s braking capability did not contribute to the crash.

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“In my view, the likelihood of fatigue causing or contributing to the sudden deviation is small,” he said, and witness observations were “not consistent with the stereotypical micro-sleep scenario”.

“Although I cannot exclude either of the possibilities favoured by the experts, I consider the steer blown tyre scenario is more likely than that of momentary inattention. 

“It is difficult to conceive Mr Hicks with his experience and approach to driving, became distracted just prior to him passing another heavy vehicle along a narrow road.”

“But even assuming he did become distracted, that does not readily explain how he could lose control such that he travelled at the angle he did into Mr Jeffery's lane.”

He said the police officers and emergency service personnel at the crash site “ought to be commended for their efforts at the scene”. 

“The conditions at the collision site were extreme and confronting,” Mr Holmes said.

Experts believe the trucks collided travelling about 80km per hour and “the damage to the vehicles was catastrophic”. 

Police suspected Mr Jeffery had been ejected from his prime mover following impact and that his remains would be located out of the prime mover's cabin. 

“Officers ... were on their hands and knees digging through the grain under lights for a number of hours to locate Mr Jeffery. Machinery was not used in this particular search due to the concern it might result in damage or destruction to Mr Jeffery's remains. 

“Their efforts continued into the early hours of 15 June 2016 under lights.”

Police eventually found Mr Jeffery at about 12:30 am at a position outside the wreckage of the Kenworth prime mover. His body had been completely covered by wreckage, debris and grain and had been damaged by the fire.

Once the scene was cleared, the wrecks were taken to a Guyra holding yard, where a month later part of Mr Jeffery’s foot was found.