The foster mother who has emerged as a person of interest in the disappearance of William Tyrrell previously declared the couple had "nothing to hide" and had been thoroughly investigated by police and was even the target of covert surveillance.
"We gave them everything. They took our laptops," the foster mother said.
Despite public questions as to why police did not probe the foster parents earlier, police who worked on the case say the family was closely looked at and brought in for questioning.
In a podcast by Channel 10 investigative journalist Lia Harris, the couple conducted extensive interviews about their case and their distress that Detective Gary Jubelin was taken off the investigation.
Jubelin also investigated the foster parents, bringing them in for separate extensive interviews with "no warning", according to Harris, and then putting a listening device in their car to hear what they spoke about on the way home.
"They said nothing incriminating," Harris said.
The foster mother has previously declared she had nothing to do with William's disappearance and although upset at the time that police treated her like a suspect, she ultimately understood it was simply part of the investigation to clear them of involvement.
The Coroner's Court recently subpoenaed notes and interviews related to Harris' Channel 10 podcast Where's William Tyrrell including discussions with the foster parents about the case.
The intense scrutiny on the couple comes as extraordinary footage has re-emerged of the foster parents taking NSW police on a "walk through" of what happened the day William disappeared.
The mother, wearing activewear, runs her hands through her hair as she describes the frantic search.
"I get to the riding school and I just think, 'he's not here'," she told police.
"Then I bring the car back up and I just run out and look for him again."
Being a person of interest does not necessarily suggest William's foster mother is a suspect.
She has not been arrested or charged in relation to William's disappearance.
Who are the foster parents?
William Tyrrell's foster mother is a wealthy professional from Sydney's north shore. She is now 56 years old.
On the day that William went missing, she was visiting the home of her mother in Kendall, NSW, when William suddenly disappeared in the middle of a game.
The foster mother and the foster grandmother were sipping tea on the ground-floor back deck when the mother suddenly declared she couldn't hear William and called him.
But police investigations have now turned to whether William could have fallen from the upper deck on the other side of the property.
The couple have led public campaigns asking "Where's William?" for years calling for public information on the case.
But when the Daily Telegraph reported in September that NSW Police had zeroed in on a new person of interest, the foster family issued an angry statement.
"Imagine waking up to an unsubstantiated article published by a large media outlet claiming a 'senior officer' within NSW Police shared that they have a NEW person of interest, while inferring that this case is on the brink of being solved," the couple said on the "Where's William" website.
"Once again we are forced to watch others objectify William for personal gain. Fake news causes more heartache for William's loved ones."