The lead investigator in the cold case of backpacker Simone Strobel has told an inquest he still believes she was probably killed by her boyfriend.

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.

Det Sgt David Mackie told the inquest at Lidcombe coroner’s court on Tuesday that he believed the most probable explanation was that Strobel was killed by her then-boyfriend Tobias Moran, who had travelled with her from Germany.

The pair had been touring the east coast of Australia with Moran’s sister, Katrin Suckfuell, and another German, Jens Martin.

Moran, who now lives in Western Australia, was charged with murder in 2022, but prosecutors opted not to proceed and the charges were withdrawn.

However, Mackie maintained in his opinion it was “probable” Moran killed Strobel and said he believed Suckfuell and Martin helped dispose of her body.

“It’s your opinion that the three Germans were involved?” counsel assisting Philip Strickland SC asked.

“Yes,” the detective replied.

Mackie said it was implausible Moran could have acted alone in killing Strobel, because of the difficulty he would have had in dumping her body undetected.

However, Strickland said there were several aspects of Martin’s evidence to German and Australian investigators which suggested he was telling the truth.

This included revealing he was told by Suckfuell that Strobel was considering returning to Sydney on her own for six months if relationship issues between her and Moran did not improve.

“That evidence, assuming it’s true, is really quite unhelpful to Tobias,” Strickland said.

He suggested that if Martin was involved, he must be a “very skilled liar” to give previously unheard evidence implicating Moran in the murder, without also implicating himself.

Mackie told the court he believed Martin was being truthful about the night’s events, only up to the point where he was involved in disposing of the body.

“He was doing whatever he could to assist in identifying who was involved in Simone’s death without implicating himself,” Mackie said.

About the time Strobel went missing, several witnesses reported hearing screams coming from the vicinity of a nearby park, a known crime hotspot where locals gathered to drink alcohol, the court was told.

The witness reports varied wildly in their details but were broadly consistent with describing a woman in fear for her life.

“Do you think it is a reasonable hypothesis that at least some of those witnesses heard a scream coming from Simone Strobel?” Strickland asked.

Mackie replied it was a reasonable hypothesis, among others, and agreed it was not consistent with the theory Strobel was killed by the German travellers at the caravan park.

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, Strickland said on Monday.

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.

The group later lied to police about their drug use and how much they had to drink on the night, as well as the depth of the dispute between Strobel and Moran, Strickland said.

Mackie will continue to give evidence on Wednesday.