Braydon Worldon's body was discovered on River Road, Wantabadgery, on December 19, 2018, by a passing motorist.

During day two of the coronial inquest into his death, his stepfather, grandfather and an engineering expert all gave evidence.

Coronial advocate Brooke Notley also revealed it was likely that Braydon had died on impact after being hit by a medium to heavy rigid vehicle.

Mechanical and biomedical engineer William Bailey appeared as an expert witness via video link yesterday morning.

Detective Senior Constable Stanley Wall asked him to provide a report about the moment of collision.

On Tuesday, Ms Notley asked Mr Bailey about his opinion that a fracture on Braydon's skull was caused by a bull bar rather than the road.

He explained that a pedestrian has no speed compared to a vehicle travelling along.

When contact occurs, the "pedestrian is accelerated to the speed of the vehicle over a very short distance".

Mr Bailey added that means they go from 0km/h to the speed of the vehicle.

"That requires a large amount of force ... the pattern of the injuries indicate where the force was applied."

Mr Bailey said the evidence, including the position of Braydon's body, the injuries he sustained and the width of the road indicate he was struck by the vehicle.

But, there was nothing to suggest he was driven over.

NSW Deputy State coroner Elaine Truscott asked Mr Bailey whether or not he could determine if the impact happened near a bend in the road.

"My impression was the impact occurred on the straight," he responded.

The magistrate also asked Mr Bailey if he could form an opinion on what "sensory perception" there would have been for the driver after Braydon was stuck.

"I expect there would be a loud noise which would be conveyed to the cabin ... I can't speculate if someone would or wouldn't hear," he said.

Next to take to the witness stand was Peter Lees, better known as Toby, who was Braydon's stepfather.

When asked by Ms Notley how he would describe their relationship, he said they were good mates.

"Braydon was a good kid. He loved the outdoors ... I was always worried about him when I first met Crystal [his mum] because he would go off wandering," he said.

"The family said 'don't worry, he's always been like that'."

Mr Lees told the court how Braydon loved coming to work with him, preferring the outdoors to school.

He added that on December 18, the pair of them had done some work in the morning but soon stopped due to the heat.

About 5pm, some friends visited to celebrate Braydon's birthday, and the four of them had some drinks.

Mr Lees then said John Blackwell, an owner of the property where Braydon lived with his mum and stepfather, called to ask for some help with a job.

"He [Braydon] wasn't too impressed that he had to go and do it," he said.

"I just said, 'c'mon mate, we have to go over and help John'."

Mr Lees said they wrapped up the job and he left Braydon behind at the sheds, which wasn't unusual.

He added he did not search for him either as it was not out of the ordinary for Braydon to be off somewhere fishing.

"Did you go out to River Road that night," Ms Notley asked.

"No," he responded.

"Can you tell us any information about how Braydon came to be there," Ms Notley asked.

"No," Mr Lees said.

"Were you involved in Braydon's death in any way," Ms Notley asked.

"Definitely not," he said.

Mr Blackwell then revealed during the inquest that he had been the one to identify the body.

He had employed Mr Lees, and saw Braydon as a "wonderful boy".

When the police needed someone to identify the body, Mr Blackwell raised his hand.

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"It was obvious to me that Crystal wasn't keen to do it. Toby wasn't keen to do it," he said.

The final witness to take the stand was Braydon's grandfather, John Worldon, who lives on Worldon Lane off River Road.

He told the court his grandson was his shadow as a child, always wanting to follow him around.

On December 19, before he heard the news Mr Worldon found his letterbox had been damaged.

Ms Notley asked him if he knew green paint flecks found on Braydon's clothes matched the letterbox, to which Mr Worldon said 'yes'.

The magistrate said to do that would suggest Braydon was cranky with him.

"Yep, he could have been cranky," Mr Worldon said. "I don't know. It would have taken a fair bit of energy."

Mr Worldon said, to his knowledge, Braydon would not have come near his property as the dogs "would have gone off" and that would have woken him.

Ms Notley said NSW Police have applied for a $250,000 reward to aid the search for answers.

Magistrate Truscott adjourned the court until today at 11am, when she will hand down her findings.

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