A child allegedly assaulted and intimidated by William Tyrrell's former foster parents can be heard sobbing and begging with them in audio played to a court.
The 58-year-old woman pleaded guilty on Monday to assaulting the child, who is not William, on two occasions in January and October 2021.
She is still fighting two charges of intimidating the victim in a series of incidents between January and August that same year.
Her 56-year-old partner, William's former foster father, has pleaded not guilty to one count of assault and one count of intimidation over alleged conduct in November 2020 and October 2021.
Neither foster parent can be named for legal reasons.
In recordings played in Parramatta Local Court on Tuesday, the child could be heard crying and begging with two carers, at one stage pleading with them to be let go.
Prosecutor John Marsh said covert recordings had been made of conversations within the foster parents' house on Sydney's north shore.
Mystery surrounds the 2014 disappearance of William Tyrrell, who was three years old when he vanished from a Kendall property belonging to his foster grandmother on the NSW mid-north coast.
Police have sought answers in the years since his disappearance, including conducting a thorough search of the Kendall property in December 2020.
Neither foster parent has been charged over that case.
Police also secretly recorded conversations in their car and during telephone calls as part of their investigation into William's 2014 disappearance.
"Investigators obtained evidence of a number of assaults and offences of intimidation,” Sergeant Marsh told magistrate Susan McIntyre.
In the recordings, the foster father is heard screaming at the child to get in their car, saying he is "done" and calling the child a "f***ing stupid little sh**”.
"We've done nothing to you," he was heard saying.
"All we’ve done is support you. We feed you, we house you. You treat us like sh**."
In a separate recording, his partner yells at the child to stop talking.
"No, you don't get to talk," she said to the youngster's cries.
"You are not talking. You have no voice until I tell you."
In another recording, she said: "I am stronger than you, I will outlast you, you will not beat me at this."
The foster mother separately said the child could "starve and die of dehydration" after being asked for a glass of water, and later threatened to hit the child with a spoon if they didn't stop talking.
In one audio segment where the child repeatedly pleaded for help packing up things in between gasps and sobs.
"I hate you!" the child yelled at the couple.
In the recording the woman asked for the child's hand and two smacking sounds can be heard.
Listening to this, the foster mother herself broke down in court on Tuesday, wiping her eyes with a tissue and leaning on her partner's shoulder
A recorded phone intercept showed the depth of the animosity between the child and the foster parents with the woman telling her partner she'd been locked out of the house.
“We’ve got a problem. We’ve got a big problem,” the man said.
“We've got a massive problem,” the woman agreed.
In a calmer conversation in the home, the foster father was heard apologising for making it seem like he wanted to get rid of the child.
“I don't like it when you do that. I don't like it when you threaten to get rid of me because I don't want to move,” the youngster replied.
In November 2021, police met with representatives from the NSW Department of Communities and Justice who took the child from the care of the foster parents.
The woman spoke with police and admitted certain aspects of the offences while the man continued to deny any wrongdoing.
The hearing continues on Wednesday.