Fan was abducted on March 17, 1999, by the men and held at a Granville Road flat in Tsim Sha Tsui after she allegedly stole $4,000 from Chan's wallet.

Police were informed about Fan's death after Chan's lover, a 13-year-old girl, told them she was haunted by watching and participating in the month-long torture of Fan and the disposal of her body.

Police recovered Fan's badly decomposed heart, lungs, liver and intestines from a plastic bag dumped on a canopy below the Granville Road apartment on May 26.

Her skull, which was missing its lower jaw bone, was found stuffed inside a Hello Kitty mermaid doll in the hallway of the third-floor flat where she had been held. A single tooth was found next to the doll.

The Court of Appeal yesterday heard that no cause of death was established due to the lack of a body and the condition of the internal organs.

Frederic Whitehouse and Andrew Raffell, representing Chan and Leung Wai-lun respectively, yesterday told the Court of Appeal that the jury had not been properly directed that Fan could have died from a self-induced drug overdose.

Mr Whitehouse told the court that shortly before Fan's death, she was seen picking up something resembling 'sugar crystals' from the apartment floor.

He said that nearly all of the apartment's occupants abused the drug Ice.

'If the experts could not find the cause of death, how could the jury?' he said.

Mr Raffell added: 'The issue here is did the beatings cause the death, or did the drugs cause the death?'

Richard Donald, for Leung Shing-cho, also told the court that in the 48 hours before Fan's death, there was evidence his client was staying with his father.

The appeal will continue tomorrow before Mr Justice Michael Stuart-Moore, Mr Justice Frank Stock and Mr Justice Conrad Seagroatt.

At the time of the original trial, the 'Hello Kitty murder' horrified both Hong Kong and the international media. In passing life sentences on all three defendants, Mr Justice Peter Nguyen said: 'Never in Hong Kong in recent years has a court heard evidence of such cruelty, depravity, callousness, brutality, violence and viciousness.'

The court heard that the three used everyday items to torture the mother-of-one for more than a month.

She was burned on the soles of her feet and chilli oil was poured on to her wounds. She was also strung up by the hands and left hanging for hours while being beaten with iron bars.

The court heard that after the beatings, as Fan drifted in and out of consciousness, the three appellants went to play video games.

On April 15, Fan was discovered lying on the floor of the seven-room apartment after the occupants returned from a disco. She was no longer breathing.

When police appeared on the floor below to investigate an unrelated rape complaint, the occupants panicked and decided to dispose of the body.

Over the next 10 hours, Fan's corpse was cut up in a bathtub. Chan cut off her head with a saw, while her muscles were stored in the refrigerator.

The court heard that at one stage, as the appellants boiled the skull to remove the flesh, they cooked noodles on the adjoining hob, stirring both pots with the same spoon.

Fan's body parts were then dumped in bins around Tsim Sha Tsui.