The 25-year-old, who cheered moments after the brutal killing, waved goodbye to his mother in the ACT Supreme Court on Tuesday as he was sentenced to 30 years behind bars and ordered to serve a non-parole period of 18 years.

He had previously admitted to jointly committing six offences, including murder, together with co-offenders during two shockingly violent invasions of Mr Waugh's unit in Watson.

Justice John Burns on Tuesday described Pikula-Carroll as "the driving force" behind the first incident in September 2016.

He said Pikula-Carroll had been upset with Mr Waugh, his drug dealer, about a failed heroin transaction involving an associate.

When no apology or solution was immediately forthcoming, Pikula-Carroll took a shotgun and two armed co-offenders, Peter Forster-Jones and Phouthakone Sikounnabouth, to Mr Waugh's place.

The trio forced their way in and unleashed carnage, badly injuring Mr Waugh and other people inside the home while demanding drugs and cash.

Justice Burns said none of the unit's occupants put up a physical resistance, but the offenders violently assaulted them anyway.

"This was intended to be retribution for the treatment of [Pikula-Carroll's] associate earlier that day," the judge said.

Six weeks later, concerned that Mr Waugh could identify them as police investigated the incident, the trio returned to the Watson unit in a bid to stop him co-operating with authorities.

This time, Sikounnabouth waited in a car as the getaway driver, while Pikula-Carroll and Forster-Jones went up to the unit.

Upon realising that Mr Waugh was barricading the entrance, Forster-Jones fired the shotgun through the front door and killed him.

Pikula-Carroll then dragged Mr Waugh's partner Marion Barr across the floor by the hair as he and Forster-Jones went inside and pillaged the place of valuables.

Among the things they stole was Ms Barr's phone, which was still connected to a triple zero call as the offenders fled.

In a recording of the call, Pikula-Carroll can be heard "cheering and yahooing" in praise of Forster-Jones, repeatedly calling him a "gangster".

Justice Burns on Tuesday said this "jubilant" display provided insight into Pikula-Carroll's lack of remorse at the time.

The judge rejected Pikula-Carroll's claims that he had only been celebrating because he feared Forster-Jones, and that he had not known that the gun was loaded or that Mr Waugh had been shot.

Justice Burns described those assertions as "simply incredible", given that Pikula-Carroll had needed to step over or past Mr Waugh's body to steal from the unit.

He said Pikula-Carroll had also replied "I know" when Forster-Jones described having "killed a c---" in the triple zero recording.

The judge went on to characterise the murder as a "cowardly" crime that had involved "extreme callousness".

He said he believed Pikula-Carroll now felt some remorse, but it was no doubt "mixed with regret" because the former apprentice chef had come to realise his actions would result in a long stretch behind bars.

He ultimately imposed on Pikula-Carroll the same sentence that Forster-Jones is serving, noting that only one had fired the fatal shot but the other had provided the gun and set all of the relevant events in motion.

Mr Waugh's parents were among those in the public gallery as Pikula-Carroll's sentence was handed down on Tuesday.

In a victim impact statement, father Dave Waugh described Pikula-Carroll as being "the instigator of Eden's brutal murder".

"Although [Pikula-Carroll] may not have fired the fatal shot, he is no less culpable than the shooter himself," he said.

Eden Waugh's mother, Elaine, said it broke her heart to know that she would never again see her son: "a kind, loving and compassionate man who abhorred violence".

"It all comes back to you, Jason Pikula-Carroll," she said.

"Not content with beating Eden with your fists and gun and cutting him with a machete in the first home invasion, you murdered [him] because he could identify you and you didn't want to go to prison.

"This was not a spur of the moment decision, but cold-heartedly planned."

Mrs Waugh finished with a message for the offender.

"I hope you remember every day the consequences of your actions," she said.

With time already served, Pikula-Carroll will be eligible for parole in March 2037.