Radina Djukich was last seen in May 1992 leaving a North Beach home, where she had been briefly living with Ronald Joseph Buckland, who paid her surety after she got into trouble with the law.

The following year, Buckland murdered his girlfriend Victoria Robinson and served 20 years behind bars for the killing.

When he became eligible for parole last year, aged 69, he was charged with manslaughter over Ms Djukich's death.

He was accused of killing her by injecting her with a substance, then burying her in a bush grave, but pleaded not guilty and was due to face trial.

He died on Thursday from cancer after tipping police off to bushland at Yanchep, where Ms Robinson's body was found.

They began searching on Tuesday, using heavy machinery and detecting equipment.

Corrective Services said Buckland had been receiving palliative care in the infirmary of Casuarina maximum security prison and died after being taken to hospital by ambulance, having told staff he was feeling unwell.

Buckland claimed Ms Djukich had run away interstate, but led police to Star Swamp Reserve in North Beach in February.

Australian Associated Press