A man who murdered his ex-girlfriend and her daughter has surprised a Sydney court by attempting a last-minute back-flip on his guilty plea, before a judge jailed him for life.

Key points: Daniel Holdom received two life sentences for his crimes

Daniel Holdom received two life sentences for his crimes There was applause from the public gallery after the sentence was handed down

There was applause from the public gallery after the sentence was handed down The judge described Ms Pearce-Stevenson's murder as a crime of "extreme gravity and appalling depravity"

In July, Daniel Holdom pleaded guilty to murdering 20-year-old Karlie Pearce-Stevenson and her two-year-old daughter Khandalyce.

Ms Pearce-Stevenson's body was found in the Belanglo State Forrest, near Sydney, in 2010 and the toddler's remains were found in a suitcase on a remote highway in South Australia in 2015.

Holdom's lawyer made a surprise request in the NSW Supreme Court on Friday to revoke his guilty plea for killing Khandalyce, saying his client had trouble "digesting" the case against him.

But in rejecting the application, Justice Robert Hulme noted Holdom had an experienced legal team and he was not satisfied the 44-year-old did not understand what he was pleading to.

There was applause from the public gallery when the sentence was handed down.

Justice Hulme said there was evidence Holdom used extreme force against Ms Pearce-Stevenson, stomped on her body, violated it in "a callous and sadistic way" and took trophy photos of it.

Holdom was given two life sentences for his crimes. ( Supplied )

"His treatment of her showed complete disdain for her existence as a human being," he said.

"To him, she was just flesh with a life that could be extinguished for his vile pleasure."

Justice Hulme said Holdom had a history of violence towards women and had shown no remorse.

Justice Hulme described Ms Pearce-Stevenson's murder as a crime of "extreme gravity and appalling depravity".

Holdom shook his head in the dock during the judge's remarks.

'His brutality will haunt us'

Justice Hulme said Holdom used Ms Pearce-Stevenson's bank account after her death and that his new girlfriend claimed the dead woman's social security benefits.

Holdom also used his ex-girlfriend's phone to text her family giving the impression she was alive, and fuelling her relatives' torment and despair at not knowing where she was.

Justice Hulme said Holdom had a difficult childhood with a brutal stepfather who violently abused him from the age of four to 15.

He said Holdom had been unemployed for some time and had a problem with drug use at the time of the murders.

The court heard he had a criminal record in NSW, Queensland and the Northern Territory.

NSW Police detective inspector Jason Dickinson holds a photo of Karlie and Khandalyce. ( AAP: Dean Lewins )

Ms Pearce-Stevenson's family released a statement describing Holdom's crimes as "despicable".

"His brutality will haunt us forever," they said.

"Nothing done to him will bring Karlie and Khandalyce back or repay the toll on us.

"Such said, he has forfeited his right to his existence.

"From now until he dies, young women and children must be protected — their safety must be paramount.

"We can no longer hold and hug Karlie and Khandalyce, but we will never stop loving them."

Daniel James Holdom has been charged with Karlie Pearce-Stevenson's murder. ( ABC News )

Outside court, the Commander of the NSW Homicide Squad Scott Cook said the families of Holdom's two victims had suffered enormously.

"They have always conducted themselves with dignity and assisted police," he said.

"I hope today brings some conclusion to the trauma they have been through."