The woman, whose name is suppressed, told the ACT Coroner's Court on Friday that the team had suspicions early on after reports of bruising to his face but believed there was nothing to go on.

The ACT's Child and Youth Protection Services closed the files on Bradyn without taking any further action.

"I look back now and I'm really embarrassed," the case worker said, breaking down on the stand.

"All my information that I thought was thorough, wasn't thorough."

She said the case had escalated.

But she asked herself if she had failed to grasp it and, as a new staff member, was overwhelmed with her workload: "Why didn't someone else grasp it?"

"I needed that help to make sense of it," she said.

"I feel like it was all on my shoulders."

She said her case load had doubled from when she began work in April that year to December.

But despite agonising over her decisions since Bradyn's death, the worker said she would not give up her work in care and protection, because the situation had shown her the importance of the job.

She said a lot of people walked away from it.

Graham Dillon, 41, killed his 9-year-old son Bradyn at their home in Jacka in February 2016 with a vicious beating. He is serving more than three decades in jail for the murder.

An inquest is examining the circumstances of his death, including what authorities knew when and the adequacy of their responses.

The inquest has heard that on November 20 that year, the boy's mother had taken him to Victoria without Dillon's approval.

While Victorian authorities tried to keep Bradyn in that state, Dillon fought the attempt at court and won, partly on the basis of a protection order that purportedly prevented her taking the boy.

Canberra care and protection workers had not verified the information from Dillon, but told Victorian authorities the order was current and that the mother had tried to "abduct" the boy before.

In fact, at the time there were no orders that prevented the mother from taking the boy.

The children were returned to Dillon's care, with the boy crying hysterically and begging not to be returned to a father that hit him.

This was communicated to the Canberra case worker on Dillon's file.

On December 9, Bradyn's mother told the junior case worker about her concerns and the threats Dillon had made to her and his ex-partner, including that he would "boil her up and eat her face".

Around this time the file was transferred to another worker.

But it was not until January 19 the following year that the authorities visited Dillon and his son at their home in Jacka.

The case worker said she did not know why there was a two-month delay between the Victorian report and the visit to the home.

The case worker earlier told the court that she and the others had suspicions about Dillon abusing the boy.

But although a file on Bradyn was opened twice in July and August 2014 after multiple reports from the school about bruises to his face, both times the case worker closed it without taking further action.

The case worker agreed that in hindsight there were other options rather than closing the file, including extending the appraisal period.

But she said that at the time there was nothing to go by.

The court has heard that a doctor after assessing Bradyn reported that most of the bruises could be explained except the one to his ear.

The worker said Bradyn had not told them it was his father causing the bruising.

She later said that in hindsight there was a lot of information on the file.

The agency had heard of mounting concerns from Bradyn's school about his unexplained absences and hand-shaped bruising to his face as well as his behaviour.

They knew of Dillon's shady past and court dealings, and his history of family violence against two former partners.

They had heard that Dillon hit the child around the head and kicked him in the bottom with a boot when he wasn't expecting it.

"But for some reason at that point we found [abuse] was not substantiated," the worker said.

The agency also had conflicting information, the court heard. The boy was clean and fed and the house was always neat and tidy. Bradyn had told them that "everything was good about his dad".

A men's crisis worker working closely with Dillon and the boy had no concerns about the man's fathering ability, the court heard.

The inquest continues in February next year.