However, an expert on Indonesian law said Australians need not be overly worried that the perpetrators of the Bali attacks would walk free. "People shouldn't be afraid of it. There are plenty of other grounds on which the Indonesians can get these people," said Tim Lindsey, an associate professor at the University of Melbourne Asian Law Centre.

Murder, arson and illegally transporting explosives were more conventional charges they could face which would also carry hefty sentences.

The principle of double jeopardy - not trying someone for the same crime twice - would not apply if the Bali bombers' appeals were accepted, as the verdicts would not be reversed but quashed, Dr Lindsey said. "That means they never existed."