Former Detective Chief Inspector Gary Jubelin this month lost an appeal against his conviction and $10,000 fine for illegally recording a person he considered at the time to be a "person of interest" in the investigation into the 2014 disappearance of three-year-old William Tyrrell.

Jubelin, who led the investigation, quit the force in 2019 after charges were brought against him. In April, Jubelin was found guilty in the Local Court of secretly recording four conversations with a man who lived next door.

Jubelin told the court he made the recordings because he feared the person might commit suicide and any statements he made would be lost.

Even though police had a warrant to install listening device surveillance on the person, this did not include Jubelin's own phone, on which he recorded three conversations in person with the man and one on the phone.

Jubelin did not ask the man's permission to record the conversations, or notify him that the conversation was being recorded.

"The police officer was found to have breached section 7(1) of the NSW Surveillance Devices Act 2007, which states it is against the law to record a private conversation without the consent of the other person," says lawyer Anneka Frayne of Stacks Law Firm.

"Even though Judge Antony Townsden agreed the officer's motivation was to help the investigation, he ruled his action breached the law," Ms Frayne said.

According to The Guardian Australia, the judge told the appeal court: "In a democratic society, those placed in a position of authority have an obligation to exercise their power lawfully. This, the appellant failed to do."

Ms Frayne said the decision shows police are not above the law. "Recording a conversation without permission carries a heavy penalty - $11,000 and a maximum five years in jail. The aim is to protect privacy.

"There are exceptions, such as if police have a warrant, if the recording unintentionally hears a private conversation, if it involves the body-worn video of a police officer, or the use of listening devices in accordance with Commonwealth law, such as the Telecommunications (Interception and Access) Act 1979."

There is a broadly worded defence in Section (3)(b)(i) of the NSW legislation that states if the principal party consents to a listening device being used, and recording the conversation is "reasonably necessary for the protection of the lawful interests of that principal party", then recording can be legal without getting permission.