The family of an Australian mother are in disbelief amid fears the mother-of-four could face the death penalty in the United States if convicted over the murder of her seven-year-old stepdaughter.

Lisa Cunningham, 43, and her husband Germayne Cunningham, 39, are accused of abusing and neglecting Sanaa Cunningham, who died from pneumonia and complications from sepsis in February 2017.

The couple are accused of zip-tying the child to a water tank in a garage at their home in Arizona and neglecting to treat a septic wound to her foot.

Lisa Cunningham, 43, (pictured) allegedly abused and neglected Sanaa Cunningham, who died from pneumonia and complications from sepsis in February 2017, by zip-tying her to a water tank in her garage and neglected to treat a septic wound to their foot

Sanaa was also made to pick up dog faeces by the pair with her bare hands and restrained in a straight-jacket-like long-sleeved shirt, the prosecution alleges.

On Monday, a Maricopa County judge ruled Lisa and Germayne Cunningham could face the death penalty if convicted.

Prosecutors allege Sanaa was unable to expel liquid from her lungs as a result of being restrained, exacerbating her pneumonia and leaving her unresponsive.

Family of Mrs Cunningham claim the former Adelaide woman is innocent, the Sunday Mail reported.

'What I know I could not honestly see her doing something like that. I really and truly believe she is innocent. She was too nice a girl,' said cousin Julie.

Mrs Cunningham's uncle, Rob Topsfield, 70, said the Americans had got it wrong about his niece who 'wouldn't hurt a fly'.

'I'm really angry with the American judicial system at the moment,' he said.

Mr Topsfield is disappointed that he can't fly over to support his niece as he is undergoing cancer treatment.

Prosecutors allege the restraints Cunningham used to tie up Sanaa (pictured) meant she was unable to expel liquid from her lungs, exacerbating her pneumonia and leaving her unresponsive

He claims Mrs Cunningham is a compassionate person who cared for her two older brothers when her mother experienced mental health struggles.

Mr Topsfield said Mrs Cunningham had tragedy in her life as her grandmother and mother died within a short period of time when she last visited Australia.

Mrs Cunningham was born in Adelaide, before moving around the country and living in Far North Queensland.

She moved to the United States in the late 1980s as a teenager and then met her first husband.

Two weeks before she pleaded not guilty, Mrs Cunningham tried to commit suicide, according to the Sunday Mail.

Lisa and Germayne Cunningham (pictured), the former of whom has lived in the USA for 20 years and comes from Adelaide, could face the death penalty following their hearing in October if found guilty

The case could create diplomatic disharmony as the Australian Government is opposed to the death penalty.

If convicted and sentenced to death, she would be the first Australian woman to face the death penalty in the United States.

According to The Phoenix New Times, Sanaa's death went unreported by state welfare agents for months before a grand jury charged the Cunninghams with 10 counts of child abuse and one of first-degree murder in December.

The couple were allowed to remain free until Monday, when judge Michael Kemp ruled prosecutors had enough evidence to justify their aim to seek the death penalty.

He said: 'There were many warning signs with regard to her need for medical attention.

'This was more than reckless behaviour. This was more than a failure to provide care and it led to the child's death.'

Cunningham and her husband Germayne Cunningham, 39, (pictured) are charged with 10 counts of child abuse and one of first-degree murder after Sanaa's death went unreported by state welfare agents for months

But Lisa Cunningham's lawyer Taylor Fox argued doctors had differing views about what killed the seven-year-old - who noted the autopsy was inconclusive as to whether Sanaa was killed or died by accident.

Mr Fox also said the accused called a doctor two days before she died, but had to wait until Monday to book an appointment.

Lisa and Germayne Cunningham, a former Phoenix policeman, have been refused bail, with a hearing date schedule for October.

Sanaa's mother, Sylvia Norwood, 38, is still grieving the loss of her second daughter, according to her lawyer Quacy Smith.

Mr Smith told the Sunday Mail it took 24 hours for his client to be notified about Sanaa's death.

'Parents don't expect to have to bury their children,' he said.

Sanaa Cunningham had pneumonia at the time of her death, and the prosecution allege the couple's neglect made her condition worse and left her unresponsive

The method of death penalty in Arizona is lethal injection, but a criminal convicted before November 23 1992 can also opt to be killed by gas inhalation.

No-one has been executed by death penalty in the state since 2014.

The Australian had lived in the US for 20 years and is eligible for $500,000 in funds from the Attorney-General - which provides support to Australians facing the death penalty overseas.