But her violent death at the hands of Josaia Vosikata had shattered not only Ms D'Addario's life, but the lives of many who knew and loved her, the ACT Supreme Court heard on Tuesday.

Vosikata, 29, strangled his former girlfriend to death in her Bruce apartment on April 19 last year before he shoved her body in the boot of a car and drove to the NSW south coast.

The pair's disappearance sparked a huge search and Vosikata was eventually captured near Bermagui on April 23.

He pleaded guilty to Ms D'Addario's murder in March and returned to court for a sentencing hearing on Tuesday.

Ms D'Addario's sister said in a victim impact statement she would never be able to forgive Vosikata for the "despicable and shameful acts" he committed, "no matter how remorseful or sorry he claims to be".

She believed Vosikata should be jailed for life, but told Justice John Burns: "No sentence you hand out will bring my sister back.

"Why should he ever be given another chance to be a member of our community when, for no other reason than jealousy, he stole from my sister everything she had at the age of 35.

"And, at the same time he murdered her, he stole everything she was ever going to have."

Another sister, in a statement tendered to the court, said it was hard to describe the "debilitating realisation" she would grow older than Ms D'Addario because of the years stolen by "one horrific and unforgivable act".

She said society had lost a beautiful and compassionate woman and she had experienced a trauma and shock so deep "it lays beyond comprehension".

"I could never have perceived we would lose Daniela in this way."

Ms D'Addario's aunt told the court it was "impossible to conceive someone who had so much to contribute had been so badly treated".

"We will move on. Dani will always be cherished.

"However, the impact of the unnatural shortening of her life at the hand of another human being can never be forgotten. The effect of this wicked and criminal act will be with us forever."

ACT Director of Public Prosecutions Jon White urged the court to impose the maximum sentence of life imprisonment for the murder and Vosikata's "premeditated conduct of revenge".

Mr White noted court documents showed Vosikata had searched the internet for "remote cottages" and "remote national parks" in the weeks before he killed, and later researched various potions to knock people out and "how to kill without joy".

Mr White said Vosikata's inability to move on with his life, and his unwillingness to let D'Addario live hers, grew his misery and rejection and resulted in his vengeful actions.

"The obsession he held for the victim led him to kill her.

"A very vibrant ... young woman has been taken in the prime of her life and that has left her family devastated."

Defence lawyer Paul Edmonds said, while a lengthy sentence was inevitable, a life sentence wasn't the only option to protect the community from Vosikata, who didn't pose a significant risk of reoffending and wasn't beyond reform.

Mr Edmonds agreed Vosikata had been "utterly obsessed" with his former girlfriend and said he "lost control" after it dawned on him they weren't getting back together.

"What's conceded, Your Honour, is a quite pathetic scenario of the accused not being able to accept the relationship was over."

He told the court his client clearly had admitted his intent to kill and acknowledged the internet searches in the lead-up to his crimes showed some contemplation.

However, he said the killing, while "heinous", lacked other aggravating factors present in murders of the worst category.

"He's no Marcus Rappel or Ivan Milat or many other offenders who've been convicted of this offence."

Vosikata sat with his head down throughout much of the hearing.

Justice Burns is expected to hand down his sentence before the end of the year.