Secret campsite recordings before arrest

Police listened to more than 5000 covert recordings of Greg Lynn in his home, car and campsites to build the case against the former airline pilot accused of killing campers Russell Hill and Carol Clay.

It's alleged the 56-year-old made comments about the deaths of the campers, which were picked up on the secret listening devices and led to his arrest in November 2021.

Mr Hill and Ms Clay vanished while camping in the Wonnangatta area of Victoria's alpine region in March 2020.

Lynn, 56, is charged with murdering the couple at their Bucks Camp campsite, sometime after 6pm on March 20, 2020. He denies the charges.

Police allege that after killing the pair he set fire to their campsite to destroy any potential evidence and dumped their bodies in remote bushland near Dargo.

They also claim Lynn returned in May and/or November that year to tamper with their remains by "burning, dispersing and partially interring them".

Detective Leading Senior Constable Daniel Passingham told Melbourne Magistrates Court that there were 5287 covert recordings obtained from listening devices in Lynn's Caroline Springs home, his car and a phone tap.

They range between one and 30 minutes in length, he said.

According to police, Lynn had conversations with himself at various locations including at home and while camping including referring to the deaths of Mr Hill and Ms Clay.

Police swooped on Lynn to arrest him after hearing on the car listening device that he was headed back to the high country. He was arrested at an Arbuckle Junction campsite on November 22, 2021.

Mr Hill and Ms Clay's remains were discovered a week later, four days after detectives ended a marathon interview with Lynn ending in him being charged.

Detective Sergeant Brett Florence and Det Passingham were grilled by Lynn's defence team on Monday about the contents of the interview, conducted over four days between November 22 and November 25.

But Magistrate Brett Sonnet, who is set to decide if there's sufficient evidence for Lynn to stand trial, granted a suppression order preventing publication of information coming from or relating to the police interview.

The suppression over significant parts of the prosecution case also includes a statement Lynn made to police in July 2020 and a covert recording taken by officers the same day.

Those pieces of evidence pose a real and substantial risk of prejudice to the administration of justice, barrister Dermot Dann KC had argued on Friday.

"The contents of these items of evidence are explosive, or may be seen as explosive in the eyes of readers or viewers," Mr Dann said, referring to the potential for sensational reporting.

Prosecutors or police are yet to reveal how it's alleged Lynn killed the couple or what motivated the murders.

Sgt Florence said on Monday that blood and biological material confirmed through DNA as being from Ms Clay was found on Mr Hill's vehicle.

An autopsy on their remains was carried out but the cause of death was unable to be determined because the only bones recovered were fragmented, he said.

Mr Dann highlighted concerns over the length of the interview, the approach to Lynn's right to silence and the approach to his legal advice.

He has previously described some aspects of the evidence as "highly inadmissible", flagging a future challenge to have details cut from the prosecution case altogether.

The hearing is set to continue on Wednesday.