Before a packed Canberra court on Tuesday, where Bradyn's mother sat watching, Dillon, 39, stood with his hands gripped behind his back and pleaded guilty to murder. And five other violent crimes committed against his son over a period of months.

Bradyn's mother and family cried at the back of the court.

It has been more than a year since February 15, 2016, the evening paramedics and police were called to the Jacka home where Dillon lived with his son.

Now, the full extent of the horrific abuse the boy suffered at his father's hands can be revealed, after a statement of facts was tendered at his arraignment in the ACT Supreme Court.

Between December 2014 and February 2016, Dillon violently and repeatedly assaulted the boy, often as punishment for some real or imagined misbehaviour, such as stealing lollies.

Dillon used his hands, fists and lit cigarettes to cause the boy broken bones, black eyes, burns, scars and bruises, the documents say.

The documents detail more than 70 separate bruises and cuts on the boy's body, from his head to his legs.

On some occasions, when Dillon was smoking in the bathtub, he called his son in and put the lit cigarette out on his skin.

Other times, Dillon would pick up Bradyn and throw him against the wall. He would assault Bradyn with a belt on his lower back.

He assaulted the boy's legs causing "dead legs". He would force Bradyn's head under the bath water so he couldn't breathe.

He would use two hands to grab the boy's throat and squeeze so tightly he couldn't breathe. The boy would pass out.

Around Christmas 2015, Dillon's violence escalated. He kept the boy inside constantly and the neighbours no longer saw him.

Dillon bashed the boy's head at least twice in two months, causing bruising and bleeding to his brain. Until a final assault on February 15 caused Bradyn's old brain injuries to bleed again.

About noon that day, Dillon had smacked the boy with a leather belt while he was bent over a table and then kicked him.

Dillon then bashed his son's head, hard enough to fracture teeth.

Bradyn fell unconscious and never woke.

"These aggregated brain injuries caused Bradyn's death on the evening of February 15, 2016," the documents say.

At the time he was arrested, Dillon weighed 70 kilograms and stood at 180 centimetres, while his son weighed about 25 kilograms.

While his son lay unconscious, Dillon took out his phone and Googled "what does it mean if someone is knock out how do you get them up".

He called a friend and said he did not know what to do, that Bradyn was making a "funny noise like he's got something on his chest, like he needs to cough".

Another Google search went "how to see if someone has a hole in there lung".

That afternoon, Dillon came and went from the house several times, once to sell an Xbox 360 for $20, to a neighbour in Bonner.

Triple-0 was called at 7.47pm, and Dillon was soon arrested.

There was cannabis, ice and amphetamine in Dillon's system when he was later admitted to jail, the documents say.

Blood-spatter stains were found throughout the house.

Bradyn's death prompted the ACT government to launch an inquiry, headed by the former director-general of the NSW Justice Department, Laurie Glanfield, and tasked with investigating systemic government failings in family violence and child protection.

The inquiry made 31 recommendations, many of which called for change within the ACT's Child and Youth Protection Services, including better sharing of information between agencies.

As well as murder, Dillon pleaded guilty on Tuesday to choking Bradyn and making him unconscious, to threatening to kill him, and recklessly and intentionally inflicting grievous bodily harm and one count of assault causing actual bodily harm.

Dillon remains in custody in the Alexander Maconochie Centre.

The case will return to court on December 14 for sentencing.