Blake Corney was killed in July 2018, when Akis Emmanouel Livas "blacked out" behind the wheel of a seven-tonne truck that was travelling about 70 kilometres an hour. The truck ploughed into the back of a Ford Territory carrying Blake and his family, as the car sat stationary in a queue at a red light on the Monaro Highway at Hume.

Livas, who has since been diagnosed with sleep apnoea, knew for years before the crash that he most likely suffered from the disorder. However, he ignored doctors' advice and failed twice to attend sleep study referrals. He also neglected to disclose the likelihood that he had sleep apnoea when he renewed his heavy vehicle licence and started a new job driving trucks shortly before the crash.

Livas, 57, is due to be sentenced next month, having pleaded guilty to culpable driving causing death in an admission that he should have addressed his sleep issues prior to the incident.

He appeared in the ACT Supreme Court on Friday, when five members of Blake's family provided victim impact statements.

Blake's mother, Camille Jago, said he had been "full of energy and vivacity" throughout his short life, and had constantly made her heart soar with love, joy and pride.

As pictures of Blake's life were shown on a screen, Ms Jago said he had especially loved Thomas the Tank Engine, music, puzzles and playing on slides at the park.

Since Blake's death, Ms Jago said she had felt lost, as if a piece of her was gone. She had taken to speaking to pictures of Blake and to his ashes in a bid to maintain some sort of relationship with him.

The impacts of the tragedy stretched into every corner of Ms Jago's life. For a long time she could not think about her younger son Aidan's future for fear he would also be killed, while driving long distances as a family was now out of the question because of the stress being on the road caused.

Ms Jago said she struggled with even the simplest of things, like choosing meals. Making Blake's favourite foods seemed wrong because he was no longer around to eat them. Taking family photos did not feel right anymore either, because Blake would not be in them.

"[Blake] is missing because he is dead, and he is dead because of Akis," Ms Jago said.

Ms Jago said she knew Livas had not intended to kill Blake, but adults had responsibilities in life and Livas had decided to ignore his, thereby robbing Blake of the chance to ever make his own adult choices.

Ms Jago told Livas that Blake "paid the ultimate price for your poor choices and lies".

"There will forever be a Blake-sized hole in my heart," she said.

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Blake's father, Andrew Corney, said it had been particularly heart-wrenching to know that Aidan, who was just two at the time of the crash, would have to grow up without his big brother.

Simple things like Aidan asking his father to play still caused Mr Corney pain, because the requests made him realise Aidan could never ask his brother to play with him again.

Mr Corney said Blake's zest for life had been on show in the moments before his death, with the four-year-old enjoying his favourite music as the family headed for Toys R Us - a destination they would never reach.

He detailed the horror of trying to free Blake from the car after the crash and seeing the inside of his son's skull - a memory that would now haunt him for life.

"There is no get-out-of-jail-free card for me in this respect," Mr Corney said.

Mr Corney said he felt disbelief, anger and fury because Livas could have behaved differently and thereby avoided causing the tragedy.

Blake's grandparents also gave victim impact statements, referring to never-ending cycles of grief.

Later on Friday, the court viewed confronting dash cam footage of the crash. Livas gasped loudly as video from his truck showed the moment of impact.

Crown prosecutor Soraya Saikal-Skea pushed for a significant sentence that would reflect the "extraordinary suffering" of Blake's family.

She told the court Livas had been on notice since 2013 about the likelihood that he suffered from sleep apnoea, meaning he was highly culpable after years of failing to act on warning signs before the crash.

Ms Saikal-Skea said the 57-year-old's prospects for rehabilitation were also poor, with the culpable driving charge marking the 51st entry on Livas' criminal record.

Livas' barrister, Steven Whybrow, conceded that Livas, who has been in custody since pleading guilty in February, must be sentenced to full-time imprisonment.

Mr Whybrow said Livas was remorseful and had acknowledged his culpability through his plea and a letter of apology.

But Mr Whybrow also said Livas had not received any medical direction to cease driving before the crash, and this was not a case where Livas had already received a diagnosis and lied in order to be cleared to drive.

Mr Whybrow said the situation was rather that Livas had failed to follow doctors' recommendations to undergo tests, something many middle-aged men would be guilty of.

Livas will learn his fate when Justice David Mossop hands down his sentence on May 8.