A registered nurse who worked at the home, Roger Kingsley Dean, will appear in court tomorrow via video link, charged with 10 counts of murder after allegedly setting the building alight in the early hours of November 18. An 11th death has also been linked to the fire.

But health officials have confirmed that the death toll has since doubled.

Authorities are embroiled in the painstaking scientific and legal task of determining whether those lives ended because of old age, illness or an act of murder.

By January 9, 21 of the 96 residents had died either during the fire or afterwards. All residents have been discharged from hospital. More have died in nursing homes since but the Department of Health and Ageing would not provide an exact number.

Should another six deaths be attributed to the fire, it would surpass the death toll in the fire in 1981 at the Pacific Nursing Home in Sylvania Heights, for which a resident was charged with 16 counts of murder.

Among those not counted in the official Quakers Hill death toll is Bill Stuttle, 74, of Marayong.

The stroke survivor was rescued from the fire but 10 days later became weak and incoherent. He was rushed to Canterbury Hospital, where his family said his kidneys began failing and his blood, urinary tract and lungs became infected. On the evening of December 2, his wife and children were summoned to his bedside. By the time they arrived, he was dead.

Mr Stuttle's son, also Bill Stuttle, is adamant the fire contributed to his father's death.

"He'd only been to hospital once in the last 18 years except for the stroke. You can't go from being healthy to being on death's door in a week and a half," said Mr Stuttle, of Londonderry.

"It could have been the fire or it could have been from the move, or a combination of both. It's too much of a coincidence to just be natural causes."

A former NSW coroner, Derrick Hand, said prosecutors could struggle to mount a case that proves, beyond reasonable doubt, that an elderly person who died after the fire would not have died regardless.

"It makes it much more difficult when they die and you can't say it's [due to] smoke inhalation or burns. That's why police would have trouble charging him with those others who died some time later. You have to show some way that the death occurred because of the trauma that they have been through. That's difficult."

A NSW Police spokeswoman said detectives from Strike Force Westall were "examining

complex medical evidence" in relation to the deaths but would not say if more charges would be laid.

The deputy director of the Victorian Institute of Forensic Medicine, David Ranson, said forensic pathologists assisting the coroner would examine circumstantial evidence and the dead person's medical history to determine the impact of the fire.

But in cases where chronic disease was already present, determining beyond reasonable doubt that fire played a substantial role in a death could be difficult, he said.

A law academic at the University of Sydney, Arlie Loughnan, a member of the criminal law committee at the NSW Law Society, said prosecutors must be able to draw a clear, unbroken link between the actions of the accused and any later deaths.

"Whether it's possible for a link to be drawn back to the accused when there's been a number of intervening factors is something that might tax the jury," she said.

If authorities cannot conclusively connect a death to the fire, families would probably be ineligible for up to $50,000 in homicide victim compensation.

But Mr Stuttle said his family's quest for information was not motivated by money. "We just want a recognition that the death was caused by the fire. We don't want anything else. It would explain what happened because we can't explain it."