A former person of interest in the William Tyrrell investigation was secretly recorded talking to his dead wife and used the words "don't tell anyone", a Sydney court has heard.
The revelation came in the case against ex-detective Gary Jubelin who is facing charges of illegally recording four conversations with suspect Paul Savage.
The retiree, who lived close to the home where William disappeared in Kendall on the NSW Mid-North Coast, was under significant police scrutiny in 2017 and listening devices were planted in his house.
Under cross examination, Mr Jubelin's former colleague Detective Sergeant Laura Beacroft on Thursday said Mr Savage would often talk to himself.
Mr Savage, who has never been charged over the disappearance of William, was recorded in August 2017 saying: "Don't tell anyone love, they're right after me. Sorry".
Detective Beacroft said she would need to see a transcript to confirm the exact words but recalled the recording.
The court heard Mr Jubelin had already confronted Mr Savage with an allegation he was covering up the accidental death of the toddler, either for himself or for his late wife, and that he was run over by a car.
In July 2017, another covert recording captured Mr Savage using the words "you're just a little boy, you're nobody" and referring to a Sydney suburb close to where William's family lived.
But Detective Beacroft agreed the quality of that recording "wasn't great" and the Tyrrell strikeforce was "divided" about whether those words were spoken.
Mr Jubelin has pleaded not guilty to contravening surveillance warrants and claimed to have had an operational need to record the conversations.
The recordings allegedly fell outside the scope of issued warrants either because the warrants had expired or they were not made on an approved device.
In the final recording which became the subject of one of Mr Jubelin's four charges, he confronted Mr Savage and repeatedly suggested he had mental health issues which "clouded" his version of events.
"This is not the way I usually talk to people in investigations, but I just can't help thinking in a tragic set of circumstances, it can be resolved," Mr Jubelin said in the recording from December 2018.
"Sometimes with mental health if the truth's distorted in your own mind, that's where it becomes problematic."
Mr Jubelin's case has revealed disagreements and tensions within the strikeforce, although the court also heard many senior officers backed his approach.
Mr Jubelin's barrister, Margaret Cunneen SC, put it to Detective Beacroft that a commander of the homicide squad, Scott Cook, said to her the investigation was "a waste of time" and police would "never get anyone for this".
"That's possibly something that was said," the witness replied.
Detective Beacroft on Thursday said she believed Mr Savage was no longer an "active" person of interest, despite there there being nothing which could rule him out.
Mr Jubelin's case was set down for five days, but is likely to be extended into next week.
