The case highlights the increasingly central role Hong Kong plays in the global drug trade, with UN data showing most major shipments of methamphetamine, also known as Ice, to Australia originate in Guangdong, where mainland and Hong Kong organised crime groups dominate the illicit drugs market.

Gao, a business student at the University of Technology, Sydney, lived with his mother and grandmother in Hurstville, Sydney. It was earlier reported that Gao's mother was in Hong Kong at the time of her son's murder.

Australian media previously reported on Gao's alleged links with Hong Kong triads.

On Tuesday, McNamara's barrister told the court, hours before the trial was aborted, that Gao had been a member of the Sydney-based Asian triad Sing Wah.

Yesterday, Justice Geoff Bellew of the New South Wales Supreme Court set a new trial date of August 18 after the surprise discharge of the 15-member jury on Tuesday, just one day after the trial started. The case is expected to last three months.

During opening statements on Monday, the court watched CCTV images that showed three men entering the shed on May 20 last year, just before 2pm. About 33 minutes later, Rogerson and McNamara were captured on CCTV dragging something heavy in a surfboard bag before lifting it into a car. Later that day they were caught on CCTV buying a heavy chain block.

In the days after Gao's disappearance, police were also looking for two men from Hong Kong who had driven Gao to the drug deal, but the pair are understood to have left Australia.

Four days after the alleged shooting, police raided the home of McNamara and found a stash of methamphetamine in his car.

Six days later, Gao's body was found by fisherman about 2.5km out at sea. His feet were bound and his body was wrapped in a blue tarpaulin. He had been shot twice in the chest.

Both men have pleaded not guilty to murder and supplying a prohibited drug.