Push for NSW child murders retrial

Police are pushing for the retrial of a NSW man acquitted of murdering two of three Aboriginal children who went missing 26 years ago.

The children - 4-year-old Evelyn Greenup and 16-year-olds Colleen Walker and Clinton Speedy-Duroux - disappeared from Bowraville on the mid-north coast within five months during 1990-1991.

The bodies of Clinton and Evelyn were discovered in bushland on the outskirts of the town, while Colleen's body has never been found.

Local man Jay Hart was tried separately over two of the murders and found not guilty in each.

Police on Thursday confirmed they're preparing a fresh application for a retrial under existing double jeopardy laws, which is expected to be presented to the Attorney-General soon.

The victims' families have long argued key pieces of evidence linking the three crimes together have never been heard in court.

On Thursday, they descended on parliament to demand a retrial of the alleged killer.

They're asking NSW Attorney General Gabrielle Upton to refer the cases to the Court of Criminal Appeal - a move which could trigger a retrial.