Missing toddler William Tyrrell's former foster parents have been cleared of lying to a powerful crime-fighting body, despite covert recordings capturing an assault against a child.
Magistrate John Arms was not convinced the foster father knowingly gave false evidence when called before the NSW Crime Commission in November 2021 as part of a joint investigation into William's disappearance.
"It is clear the issues that were raised in relation to these offences are matters of an ancillary nature to the basis of the investigation," the magistrate said on Tuesday.
The foster mother was previously acquitted of giving false or misleading evidence to the commission in November 2022 about the same "ancillary" matter.
She also dismissed suggestions at the commission she had found William dead, potentially after falling from a verandah, and taken charge of a "situation beyond remedy".
The officer-in-charge since 2020, Detective Sergeant Andrew Lonergan, told Sydney's Downing Centre Local Court it was one of multiple theories in the toddler's disappearance.
"We simply don't know what happened to him that day," he said on Monday.
He confirmed a brief had been given to prosecutors recommending charges of perverting the course of justice and interfering with a corpse, which have not been laid.
The foster father pleaded not guilty to five charges of knowingly giving false or misleading evidence at a hearing, relating to questions about the foster mother's physical contact with a child in their care.
The child is not William, who vanished from his foster grandmother's property at Kendall on the NSW mid-north coast in 2014 when he was aged three.
The foster mother pleaded guilty in September to assaulting the child.
"I can't believe I did that," she told her husband on the same morning she kicked the child.
None of the people involved can be legally named.
Surveillance warrants were granted for police to monitor the couple's home and telecommunications in December 2020.
The devices captured what police prosecutor John Marsh called a "significant day in the household" in October 2021.
"She kicked me," the child told the foster father in a recording played to the court.
The foster father was so concerned about the incident he returned home shortly after leaving the house to discuss it with his wife and should have remembered it when he faced the commission, Sgt Marsh told the court on Tuesday.
"He was lying to cover the fact that his wife had assaulted a child in their care," the prosecutor added.
Some of the charges related to ambiguous questions and answers, while other responses lacked the definitiveness to constitute a lie, the magistrate said.
The foster father answered "no" when asked if his wife had ever "harmed" the child.
It was not clear what "harmed" meant and there was no evidence before the court of "specific harm being caused", Mr Arms said.
Asked if she had kicked the child, the foster father said he could not recall, and answered "no" when asked if he could recall the child telling him she had.
It was clear on the "stressful day" the kick occurred that he was made aware, as captured in the covert recording, Mr Arms said.
However, more than three weeks later, after the additional stress of being summoned to attend the commission and without having his memory refreshed with the recording, there remained a reasonable possibility he mistakenly gave false evidence, the magistrate added.
Det Sgt Lonergan said on Monday the former foster father had been eliminated from suspicion of having anything to do with William's disappearance, "to date".
Both foster parents deny any involvement.
Another man pursued as a suspect by investigators was awarded $1.8 million in August following an unsuccessful appeal against a NSW Supreme Court decision that he was maliciously prosecuted on other charges, which described police allegations against him as "concocted and false".
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