Former senior detective Gary Jubelin is about to learn whether his appeal against convictions of illegally recording conversations during the William Tyrrell investigation is successful.
The NSW detective resigned from the police force last year after allegations of misconduct had him removed from the Tyrrell case in March.
Following a 10-day hearing earlier this year, Jubelin was found guilty in April of illegally recording four conversations with Paul Savage in 2017 and 2018, and fined $10,000.
Mr Savage had lived on the same NSW mid north coast street as then-three-year-old William when he went missing in September 2014, and became a person of interest in the case.
Jubelin's lawyer Margaret Cunneen SC said he did not breach the elderly man's privacy during the first three phone recordings, because the NSW Supreme Court had already issued warrants that allowed police to install listening devices in his home.
The fourth tape was made in December 2018 when Mr Savage invited Jubelin into his home, after the warrants had expired.
The Crown has argued that acquitting the high-profile former detective could entitle every police officer to bypass the law around listening devices.
John Bowers, representing the Crown, said the recordings were part of an ongoing investigation and were made for operational reasons.
"In those circumstances, there's no room for him to rely on the defence that he had to make them because it was reasonably necessary to protect his personal lawful interests," Bowers told the District Court in August.
Judge Antony Townsden is due to deliver his decision on Friday.
