An Adelaide father, jailed for the murder of his partner, drove the couple's two-year-old son to buy the cement used to bury his mum in the backyard, a court has heard.
Neil Archer is serving a head sentence of life in prison and a 22-year non-parole period for the murder of Jody Meyers, 20, whose body was found under a concrete slab in August 2015.
His mother Margaret Archer appeared in the South Australian District Court on Wednesday, after earlier pleading guilty to one count of assisting her son.
The court heard Ms Meyers and Mr Archer's young son was in the back seat of the car while Mr Archer drove to buy the cement used to bury the boy's mother.
The toddler would also have been in Ms Archer's house while his mother's body was lying unburied in the backyard.
After a family barbecue, Mr Archer strangled Ms Meyers following a heated argument sparked by his concerns her family was trying to break them up.
He took her body to his parents' home near Mannum, east of Adelaide, and buried it under the floor of the toolshed before returning the next day to cover the grave with fresh concrete.
She had been missing for a month before police found her remains.
At the time, Ms Archer told police and the media Ms Meyers had "just taken off".
The court on Wednesday also heard the woman cried "crocodile tears" after helping her son conceal the murder and burial of his partner.
In sentencing submissions, prosecutor Peter Longson tendered a video recording of a television interview with Ms Archer begging Ms Meyers to come home, for her two-year-old's sake.
"We miss her, we want her to come home or at least contact someone," she told reporters following the woman's 2015 disappearance.
"We tell him mummy's gone shopping, she'll be home soon, which we hope she is ... Her son needs her, he needs his mum."
Mr Longson told the court on Wednesday Ms Archer's pleas were insincere.
"She wasn't worried about anybody but Neil or herself and these crocodile tears and a call for Jody to come home," he said.
"We can only imagine what must have been said to that child who was looking for its mother," Mr Longson said.
It was previously alleged Ms Archer used the dead woman's bank card to steal $250 from her account, which she used to buy the concrete to cover Ms Meyers' body.
Judge Paul Muscat asked: "Why did it take so long for her to plead guilty?"
Defence counsel for Ms Archer said she understood the seriousness of her offending and had no relevant prior convictions, but could not explain her late guilty plea.
The prosecutor told the judge Ms Archer's role was not a submissive one, nor was it an isolated act, rather it was a continuation of actions and lies to help her son get away with murder.
Judge Muscat remanded Ms Archer in custody for sentencing on March 8.
If you or someone you know is suffering from sexual or domestic abuse, don't suffer in silence, call the National Sexual Assault Helpline1800 RESPECT: 1800 737 732 any time of day or night.
Victorian sexual assault crisis line: 1800 806 292