The "senseless" killing has left the family of victim Frankie Prineas "shattered", the ACT Supreme Court heard on Friday as killer Jayscen Anthony Newby sat in the dock looking disinterested.

Newby, 27, pleaded guilty earlier this year to the murder of Mr Prineas, also 27, admitting he had intended to seriously injure the victim when he ultimately killed him.

Agreed facts tendered to the court on Friday reveal that Mr Prineas was meeting the woman, who cannot be identified, for the first time when he was fatally wounded in January 2020.

The pair were in bed at the woman's home in Charnwood early one morning when Newby, who had been out drinking with friends, let himself into the property and grabbed a knife from a kitchen drawer.

Without saying a word, he entered the bedroom and attacked Mr Prineas, stabbing him repeatedly and accidentally cutting his own thigh in the frenzy.

Mr Prineas went into cardiac arrest in an ambulance en route to Canberra Hospital and could not be resuscitated.

Newby handed himself in at the City Police Station several hours later, and has remained in custody ever since.

Mr Prineas' father, Victor Prineas, told Chief Justice Helen Murrell on Friday that his mind turned every day to how his terrified son must have suffered.

He described Mr Prineas as a kind, loyal, caring and sentimental young man whose dreams had been snatched away.

"I loved him with every ounce of my being," Victor Prineas said.

"My son was a good man. He never hurt or brought harm to anyone.

"To have his life taken away by such a coward is just senseless to me."

Victor Prineas described his son's murder as "a vicious and cowardly act", and said Newby must be stopped from committing more "atrocious" crimes.

"The defendant had no regard for my son's life," he said.

"He deserves no mercy."

Mr Prineas' mother, Phillipena, broke down as she told the court it haunted her that she had not been there to protect him in his final moments.

"I feel as though I let my son down," Mrs Prineas said.

"This is my struggle and I live with it every day."

Mrs Prineas said her family was "shattered", and gave a moving insight into how the family dog still sat by the front door waiting for her son to come home every day.

"You have unjustly imposed a life sentence on my family, and now I hope you receive an appropriate penalty," Mrs Prineas told Newby.

"I will not allow this monster to destroy any more of my family."

Mr Prineas' sister, Paula, was overseas when she heard her brother had been murdered.

She told Chief Justice Murrell she had cried on the floor of an airport when she realised her "first real best friend" was gone.

"[Frankie] was extremely goofy and funny," she said.

"To explain our friendship, I would be here for hours."

Natalie Leighton, a cousin of Mr Prineas, said there was now "a gaping hole that can never be repaired" in the family.

More than 600 people attended Mr Prineas' funeral, his aunt and godmother Angela Notaras told the court, highlighting the fact many lives had been irreparably changed.

Ms Notaras said she had gone to all of Newby's court appearances, and described it as "horrifying to witness" the killer's demeanour and lack of evident remorse throughout.

She said Newby looked "bored" as he sat in the dock with his "freshly shaved mohawk".

"I am terrified that he is capable of hurting other people in this community," she said.

Chief Justice Murrell thanked those who read victim impact statements, saying the court acknowledged their grief and loss.

She said it was "only natural" for them to feel angry, and cautioned that no sentence she imposed on Newby would cure their pain.

"The court does not sentence out of anger," the judge said.

"The court does not sentence to achieve vengeance."

Chief Justice Murrell said she planned to sentence Newby on June 2.

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