DNA experts in the United States are providing NSW Police with new clues on some of the state's most baffling missing persons cases and unidentified human remains.

The cases include bones from at least two people found in sand dunes on Sydney's Kurnell peninsula in 2007 and remains located near Ballina on the north coast.

Unsolved homicide squad police believe the north coast bones, found at an undisclosed site, may be those of missing 31-year-old Lennox Head mother-of-two Bronwyn Joy Winfield, last seen at her home in 1993.

Scientists at Orchid Cellmark in Dallas, Texas, have spent the past two months examining 31 exhibits of bone and tissue specimens, and a further 15 saliva swabs taken from relatives of missing persons.

The samples were delivered to them by Detective Sergeant Damian Loone, of The Rocks station, who has spent the past 12 years investigating the disappearance and suspected murder of northern beaches woman Lynette Dawson.

The only possible clue about the fate of the 34-year-old Bayview mother, who went missing in January 1982, is a pale-pink cardigan found near a hole that was dug for a swimming pool on her property.

Detective Sergeant Loone took the cardigan to the US to try to match Mrs Dawson's DNA with a sample from one of her daughters.

The detective is expected to return to the US in the next month to reclaim the exhibits and DNA results, which will be screened against those from relatives of other missing persons.

Saliva swabs taken from Mrs Winfield's daughters will be compared with DNA from bone fragments found on the north coast amid renewed inquiries by police in the past three months.

Mrs Winfield, who a coronial inquest declared dead in 2002, was reported missing by her estranged husband 11 days after she was last seen at her home.

The US tests could also reveal the sex of at least two people from three separate sets of bone fragments found in dunes in 2007 during land clearing preparation for the construction of the Sydney desalination plant at Kurnell.