Investigators need to rely less on testimony and more on following money trails and other evidence if modern slavery convictions are to improve, a new report suggests.
Just a handful of cases are proven each year, given the difficulty of prosecutions, challenges identifying offending, and an over-reliance on victims speaking up.
It is clear that modern slavery - which includes offences like forced marriage, exit trafficking, servitude, and forced labour - is under-reported in Australia.
The case of Jerwin Royupa is one example which does not appear in statistics.
The 21-year-old Filipino arrived in Australia in 2019 on a training visa to work at an outback NSW winery.
Asked to work 60-hour-weeks doing manual labour on non-agreed pay without the training he was promised, he became fearful when he didn't have access to his passport.
Five weeks into his stint, Mr Royupa died from injuries from exiting a vehicle being driven by his visa sponsor, who threatened to take him to the airport or the police.
It took a coroner's probe to establish evidence around Mr Royupa's death.
Alison Rahill, the executive officer at modern slavery remediation outfit Modus 8.7, said the case displayed "all the hallmarks of the footprint of deception".
"There is a large cohort of people out there who are not being identified or supported as in modern slavery situations," she told AAP.
A report from the Australian Institute of Criminology, commissioned by the Anti-Slavery Commissioner and out on Tuesday, again showed the challenges around prosecuting the suite of crimes.
Only 41 people were convicted of modern slavery crimes in the two decades to 2025, including five in the most recent year, when 420 reports were made.
The most common modern slavery allegation is forced marriage, with 118 reports according to the Australian Federal Police, followed by sexual servitude and exit trafficking.
Anti-Slavery Commissioner Chris Evans said the number of allegations showed "the breadth and persistence of modern slavery in Australia".
These crimes are almost always (88 per cent) committed by men with almost always (87 per cent) female victims.
The report suggests Australia's "central" reliance on testimony may prevent investigations being seen through.
"Victims and survivors may not wish to participate in a criminal justice process for a number of reasons, including not identifying themselves as victims, lacking trust in the criminal justice process, and viewing cooperation as inconsistent with their best interests," the report says.
That testimony can also be wrong due to fear, trauma-related memory issues or a desire to protect themselves or family members' visa status.
"[In other countries] there is a much stronger focus on following the money trail and looking at other forms of digital evidence," one anonymised stakeholder, quoted in the report, said.
Ms Rahill said it was also crucial that victims' first experiences with Australian law enforcement felt safe.
"If you're sitting in an interview room when your workplace has been raided by police with guns ... that's terrifying even if you've done nothing wrong," she said.