The woman, who cannot be legally named, was examined by the NSW Crime Commission for two days in November 2021 over the three-year-old's disappearance.
Michael Barnes accepted William Tyrrell's foster mother would not have intentionally harmed him. (Bianca De Marchi/AAP PHOTOS)
Commissioner Michael Barnes told her at the time that the purpose of the private hearings was to recover William's body and to allow it to be respectfully interred, allowing loved ones to move on.
"We all accept that you love William and would not have intentionally done him any harm - we also understand that accidents can happen," Mr Barnes told the foster mother.
"If that's what occurred on the day William went missing, this is your chance to safely and privately explain that."
Footage of the interview was played on Thursday to an inquest investigating the three-year-old's disappearance, which has for several days been examining a police theory the foster mother disposed of the toddler's body after he accidentally fell from a balcony.
Police alleged the foster mother's motive for hiding his body was that she feared another child under her care would be taken away.
The toddler - who was last seen wearing a Spider-Man costume - went missing while playing on the verandah at his foster grandmother's home in Kendall, on the NSW mid-north coast, on September 12, 2014.
The woman, who cannot be identified, has always denied any involvement in his disappearance.
Under questioning before the Crime Commission, she was grilled about what happened in the moments before William vanished.
William Tyrrell's foster mother has always denied involvement in his disappearance. (Dan Himbrechts/AAP PHOTOS)
She told commission counsel Sophie Callan SC about going inside to make tea for her mother and hearing the toddler roaring while playing "daddy tiger" outside.
He had also been jumping from the patio and playing a dice game.
Suddenly, there was silence, the foster mother said.
"I say to mum 'that's too quiet' and then I get up and I walk over and I can't see him," she said.
Asked about how long it was between when he stopped making a sound and when she went to look for him, the foster mother was unable to give a concrete answer, instead saying it was between five and 10 minutes.
A focus of the examination was a drive she said she took to a nearby riding school while searching for her foster son soon after he vanished.
A truck driver who claimed he had seen her on a road near the foster grandmother's home on the day of William's disappearance was also being examined by police, Ms Callan said.
Footage of that line of questioning is yet to be played to the inquest.
William Tyrrell's biological mother (right) was present when the footage was played in court. (Peter Rae/AAP PHOTOS)
William's foster parents and his biological mother were present at Lidcombe Coroners Court when the footage was played on Thursday.
Truckie Peter Bashkurt gave evidence at the inquest on Wednesday but did not say any of the vehicles he had seen matched the grey Mazda owned by the foster grandmother.
No one has been charged over William's disappearance and a $1 million reward for information stands.
A decade-long investigation has involved hundreds of persons of interest and dozens of searches.
