Police sent undercover officers to elicit a confession from the former boyfriend of backpacker Simone Strobel, but the lead detective on the case believes the then murder suspect “twigged” to their efforts.

Strobel’s naked body was found hidden under palm fronds at a sports ground in Lismore, in the New South Wales northern rivers region, in February 2005, six days after she was reported missing.

Her then boyfriend, Tobias Moran, who now lives in Western Australia, was charged with murder in 2022. But prosecutors opted not to proceed and the case was dropped, with $190,000 in compensation ordered to be paid.

Det Sgt David Mackie on Wednesday told an inquest into Strobel’s death he believed Moran knew police were probably secretly recording him.

After a $1m reward was offered for information in 2020, an undercover officer going by the name “Sophie” made contact with Moran, the NSW coroner’s court was told.

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She told Moran her brother had cancer and was given only two months to live, and he wanted to confess to the murder in order for his family to get the reward money.

But Moran told her the plan would not give peace to Strobel’s family and would leave those responsible still at large, the inquest was told.

“That wouldn’t be any help to me,” he said in the recorded conversation. “It wouldn’t solve the case.”

Mackie said he believed Moran “twigged very quickly” to the ruse.

“There’s been a number of covert operations conducted,” he said. “It was fairly obvious from some of those recordings that Mr Moran was very aware that conversations were likely to be recorded.”

The inquest heard earlier secret recordings of conversations between Moran and his wife, Samantha, did not elicit any admissions.

Efforts involving two undercover officers posing as convicts who spoke to Moran after his arrest were also unsuccessful, the court was told.

At the time of her death, Strobel had been touring the east coast of Australia with Moran, his sister Katrin Suckfuell and another German, Jens Martin.

Mackie previously told the inquest in his opinion it was “probable” Moran killed Strobel and he also believed Suckfuell and Martin helped dispose of her body.

Moran’s lawyer Tim Game SC grilled Mackie over several aspects of the investigation, including the degree to which other suspects were considered.

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“This is actually quite a dangerous place for a woman to go at this time of night,” Game said.

Counsel assisting Philip Strickland SC earlier told the inquest that on the night Strobel went missing several people known to police were drinking in the area.

On the night of the disappearance, Strobel’s group drank heavily in a hotel and continued to consume alcohol and smoke cannabis after returning to their campground, the court was told previously.

The group told police Strobel left their campsite after becoming annoyed with Moran.

“All three of them said Simone left the caravan park and they never saw her again,” Strickland said.

Mackie agreed the initial investigation concentrated on Moran and lies told by him, including downplaying a heated dispute with Strobel, were given significant weight.

“Those lies, on your admission, heavily affected the course of the investigation,”Strickland said.

The inquest will continue on Thursday.