Coroner Margaret Hunter fought back tears while handing down her findings on Thursday in the inquest started three years go.

She was praising Bradyn's mother, a woman desperate but who was not listened to.

Ironically, Ms Hunter said, she had to corroborate her story while the cunning and manipulative Dillon was never asked to corroborate his allegations against her.

"I commend you for everything you did to save [Bradyn]," she said.

The murder of the quiet, polite little boy shocked the Canberra community to its core.

On February 16, 2016, Dillon laid his hands on him for a last time, killing him with a final, fatal beating.

It was the culmination of years of torture. Of cigarette burns to the boy's skin, broken teeth and fractured ribs, bruising, and choking, and of holding a small blonde head under the bathwater.

Dillon was jailed in 2018 for more than 41 years for the murder and for vicious attacks on the boy's stepmother.

Dillon is fully, wholly responsible for the murder of his son.

But the community was not finished analysing, picking apart what had happened, desperate for answers about what could have been done to save the boy.

An inquest was opened soon after he was jailed. Dillon declined to participate.

The inquest heard that Bradyn's teachers had made multiple reports about bruising to child protection agencies. And often he just never came to school.

Despite the numerous reports hinting at abuse, none could be said to be a "precursor to what eventuated", Ms Hunter said.

The coroner found the multiple reports made about the boy did not reveal a need to remove him from Dillon's care, and that the master manipulator Dillon had deceived the agencies.

Six months before Bradyn died, the reports dried up.

His worried teachers were left wondering after Dillon lied and said the boy had been re-enrolled elsewhere when really he was just being hidden at home.

The coroner said that Child and Youth Protection Services, managing 18,600 cases last year, perhaps missed the rolling harm of domestic violence on the boy, that they should have investigated Dillon's lies more thoroughly, that a more experienced caseworker could have been assigned to the case.

The child protection authorities put great weight on what Dillon told them, and little if any weight on what Bradyn's mother and step-mother told them about the domestic violence perpetrated by Dillon.

The two women, themselves victims of his abuse, were not believed, because of their perceived ulterior motives to win family law proceedings, the coroner said. There were no family law proceedings for either of them, that was just another of Dillon's lies.

Authorities failed to take action on multiple occasions, the inquest found.

These were the "sliding doors" moments, the coroner said, lost opportunities where the boy slipped from the view of authorities.

But she said it would be improper to speculate about what would have happened had those moments been different.

It was six months between the agency's last contact with the boy and his death. By then Dillon was blocking the outside world from contact with his son.

"No one could have predicted the outcome that eventuated," Ms Hunter said.

"It is my view that no one could have predicted that Graham Dillon would murder his son."

Despite the coroner's findings, with witness after witness shedding tears during the inquest and even the coroner herself in handing down the decision, those who work in Canberra's community services no doubt hold that weight of responsibility heavier since Bradyn's death.

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