The cold-case murder of a young woman whose body was dumped in a NSW river two decades ago has been raised during the inquest into the disappearance of William Tyrrell.
Frank Abbott is one of the hundreds of "persons of interest" in the disappearance of three-year-old William, who vanished while playing at his foster grandmother's home in Kendall on the mid-north coast in September 2014.
Abbott was questioned over William's disappearance in late 2019, with detectives also searching a local sawmill close to where Abbott once lived.
The inquest on Wednesday heard of another disappearance - that of Margaret Cox, a 37-year-old woman last seen near the Big Oyster service station on the Pacific Highway on December 19, 1996.
William Tyrrell's disappearance remains unsolved. Source: AAP
A fisherman found her body in the Manning River near Oxley Island two days later, with a coroner subsequently ruling Ms Cox was killed by blunt force head injuries.
Iris Northam, aged in her 70s, on Wednesday told the inquest how she noticed scratches on Abbott's arms after Ms Cox went missing.
Mrs Northam's husband had been a friend of Abbott's since the days when the couple employed him in their scrap metal business.
"Both of them were keen punters so they'd talk about this race, this horse and they just kept it on," she told the NSW Coroners Court.
In 1996, three days after Ms Cox went missing, the Northams dropped into Johns River and noticed Abbott sporting large scratches on his arm.
"(My husband) said 'What happened to your arm?' and Frank just said 'Oysters'," Mrs Northam told the NSW Coroners Court.
"But they didn't look like oyster scratches to me.
"They're more than just random scratches. These were more probably seven or eight marks on the arm, more like finger marks ... (something) had gouged skin out."
In a police statement tendered at the inquest, Mrs Northam describes the "gouge marks" as "long and straight" and looking "a few days old as they had a kind of feisty look that wounds get before they start to heal".
She told the inquest Abbott never said he had anything to do with Ms Cox's death.
Police wouldn't confirm if Abbott had ever been questioned or ruled out as a person of interest but confirmed the case remains open and is now with the unsolved homicide unit.
"Local detectives conducted an extensive investigation, but after exhausting all lines of inquiry, the matter was presented to the NSW Coroner in 2010," a spokeswoman told AAP on Wednesday.
"During the inquest, a number of significant persons of interest were identified, but no one has been arrested for Margaret's murder."
Mrs Northam told the inquest she was aware Abbott was charged and acquitted in the early 1990s of the murder of a 17-year-old schoolgirl in 1968.
Abbott is representing himself at the inquest via video link from a Cessnock jail, where he's held on an unrelated conviction.
He is expected to give evidence before the inquest ends on 20 March.
