Travelling at 70km/h, the medium-rigid tipper hit the family car with such force that four-year-old Blake - who had been singing along in the back seat to his favourite music at the time - died instantly from a brain injury.

The lives of his parents Camille and Andrew, and his brother Aidan, have been in a state of suspension since that day in July, 2018.

"I absolutely feel like I am treading water, stuck in limbo," Mr Corney said.

"Blake was four years, two months and five days old when he died. Aidan is now older than Blake was. He's at preschool and loving it, and Blake never got that opportunity. It's incredibly difficult."

On Monday, a court will hear the findings from a coronial inquest into Blake's death which examined whether this tragedy could have been prevented and what might be done to stop similar horrors occuring.

ACT Chief Magistrate Lorraine Walker, acting as chief coroner, will use evidence gathered from a range of experts over the year-long inquiry, including from the Australasian College of Road Safety, to inform her report for the ACT government.

The Corney family will sit through the hearing - expected to take place over two days - while the story of what happened to Blake is replayed and Ms Walker's questions to the experts are answered.

Mr Corney will once again retell the horror of what unfolded that day. The events were so traumatic that the police officers at the scene have since been assigned to different roles in the force. Photographs of Blake's body taken by the forensic team and used as evidence have been sealed by the courts to prevent further trauma.

Mr Corney will recall how directly after the crash, about 9.30am, the driver of the truck that hit them, a delivery truck en route to a Canberra landscape supply facility, was heard repeating to a number of people: "They cut me off, I couldn't stop."

The driver of the truck, Akis Emmanouel Livas, a convicted rapist who had a slew of prior driving offences before he killed Blake, is serving a three-year-and-three-month jail sentence for culpable driving. He will be eligible for parole next May.

Livas, 57 at the time, had renewed his heavy-vehicle driver's licence in the months prior to the crash. He had failed to follow multiple directions from doctors to be tested for sleep apnoea, and had failed to notify his employers of his suspected condition.

He has since been diagnosed with very severe obstructive sleep apnoea, by the same specialist he was referred to while serving time in 2017 but failed to follow up with. That specialist noted he should not have been operating a motor vehicle.

The family's Ford Territory - with Mr and Mrs Corney in the front seats, their two sons in the back - had been stationary at the lights for about 16 seconds when it was hit, while another nine vehicles had been queued in front of it. The dashcam footage from Livas' truck showed they were visible from a distance of 344 metres before he ran into the back of them.

Whether or not sleep apnoea was the cause of the crash, Mr Corney said he hoped the coronial inquiry would address how Livas' medical history had gone unchecked.

As part of the coronial inquest, Chief Magistrate Walker, police, ACT government representatives and the Corney family received a demonstration from automotive-safety business Seeing Machines.

Seeing Machines is regarded as a world leader in technology that tracks the gaze of drivers' eyes, head position, eyelid movements and pupil size to detect whether drivers are drowsy or distracted. The technology warns drivers when they are distracted, or alerts site managers for direct intervention.

This week's court proceedings are also expected to include a cost-benefit analysis of legislating the installation of automatic braking technology in trucks. The federal government has proposed the introduction of the feature for all new vehicles from 2022, but the cost of retrofitting existing fleets means they will likely stay on the road without the safety precaution.

Mr Corney is advocating for the introduction of safety technologies.

"It's cost versus the chance of people dying; I could reflect that back to the current Covid environment," Mr Corney said.

"There are many people who don't want to shut down, because they want businesses to keep running, but on the same token in countries that don't shut down, many, many more people die."

Chief Magistrate Walker's report, in her capacity as chief coroner, will likely take several more months to prepare. Should she make recommendations for change, the ACT government will then have the final say on whether those recommendations are implemented.

With the third anniversary of his son's death approaching, Mr Corney said he had returned to work part-time but things hadn't gotten a whole lot easier.

"Every day I spend a lot of time thinking about Blake - how I found his body in the car, the crash, the process after and the fact that the perpetrator said he was not guilty," he said.

"All that stuff wraps up and makes it difficult to move on. That sort of stuff will live with me I suspect forever - same with Camille."

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