Accused Aussie killer mum: 'I had to drown my babies'

The mother charged with murder and attempted murder pictured with her two sons, aged 8 and 5, before she allegedly tried to kill one and drowned the youngest.

A New South Wales mother who drowned her two young sons in a river, killing the five-year-old, was delusional and trying to save them from a worse fate, a court has heard.

The 28-year-old woman, who can't be named for legal reasons, is on trial for the murder of her youngest child and the attempted murder of her eight-year-old son, in the Murray River at Moama on March 2, 2017.

In Wagga Wagga Supreme court this morning, the woman sat in the dock clutching at a white plastic sick bag and twirling the ends of her plaited hair before pleading not guilty to both charges by way of mental illness.

In his opening address, defence barrister Eric Wilson said the woman believed she was saving her children by killing them. The court heard she was delusional and believed she was "going to be raped, tortured … and had to prevent her children from witnessing that … or they would be killed themselves".

"She was suffering from a seriously disturbed mental state," Wilson said.

"She thought she was saving them from being killed (in a worse way)."

Crown Prosecutor Max Pincott told the court that the mother had taken her then five and eight year old sons to the riverbank and then forced them underwater. A witness who heard screams ran to the river and saw the older boy being attacked by a dog. He carried him away and the boy said words to the effect of: "I think I'm the only survivor", the court heard.

The child was taken to hospital for treatment of dog bites and pneumonia from the attempted drowning. The court heard he told police: "Mum told me to put my head in and she dunked me in there and I was starting to suffocate as she was hopping on me … and then I got out … and my mum dunked my brother … and the dog started biting me."

The five-year-old boy's lifeless body was found in the river two days later following an extensive search by authorities.

A witness who heard screams ran to the river and saw the older boy being attacked by a dog. Photo / Herald Sun

The court heard that on the morning of the killing, the woman appeared angry and had called her mother and told her: "You won't see us anymore". Later that night, local resort owner Michael Falzon saw the woman walking into his work premises and crying, about 9pm.

The witness observed that the woman's pants were ripped below her knee and so asked if she was all right.

"She answered: 'I drowned my babies'," Pincott said.

"When asked what she meant, she replied: 'I had to drown my babies'."

Falzon then took the woman to the police station upon her request.

"He observed on the way to the police station the accused was crying and saying 'my babies my babies'," Pincott said.

The trial continues.