The NSW parliament has one last chance to clear the path to justice for three Aboriginal children who went missing in Bowraville almost 30 years ago, a Greens MP says.
David Shoebridge is pushing to change the state's double-jeopardy laws after the High Court earlier this year refused to hear an appeal relating to the children's suspected killer.
He presented a bill to the NSW upper house on Thursday as the victims' family members and supporters watched from the public gallery and rallied outside.
"This is the third time I've presented to this place a law to reform the laws of double jeopardy," Mr Shoebridge told parliament.
"This is the third time that those families have come here and asked the members in this place to clear their path to justice - and I think we should be clear, that this is the last time.
"The chance for justice is now and it will not come back."
Four-year-old Evelyn Greenup, Clinton Speedy-Duroux, 16, and Colleen Walker, 16, disappeared from the northern NSW town over a five-month period from September 1990.
The man, who can't be named for legal reasons, was acquitted of Clinton's murder in 1994 and of Evelyn's murder in 2006.
Jasmin Speedy, Clinton's cousin, said she was happy efforts were ongoing but "we just continue to be knocked down so the optimism we've had along the way has kind of diminished".
"But, you know, we're still here, we're not going to go anywhere, we'll continue to fight for justice for the Bowraville mob."
Under NSW double-jeopardy laws revised in 2006, a person can be tried for the same crime for which they have already been acquitted provided there's fresh and compelling evidence.
Last year the government unsuccessfully argued in the NSW Court of Criminal Appeal that there was fresh and compelling evidence - related to the disappearance of Colleen - which justified overturning the two acquittals and a new single trial on three murder charges.
The High Court in March refused to grant special leave to the government to appeal the decision.
Mr Shoebridge on Thursday told parliament his bill sought to expand the definition of fresh evidence and to allow a second retrial application to be made in exceptional circumstances.
He said his third attempt to change the laws came after they had been tested in the courts.
"I know that politics is politics and this will be hard ... but I'm more hopeful now than I've ever been," he said.