WARNING: Disturbing content

A woman who killed her five-year-old son and tried to drown his nine-year-old brother by holding them under water in a New South Wales river has been found not guilty on the grounds of mental illness.

In Wagga Wagga court this morning, Justice Richard Button delivered a “not guilty” verdict on one count of murder and another of attempted murder, at the trial of a 28-year-old woman, who can’t be named for legal reasons.

The judge found that the woman drowned her youngest child and attempted to drown her eldest in the Murray River at Moama, on March 2, 2017. But he said that mental illness — including borderline personality disorder and a major depressive condition — had caused her to “fail to appreciate what she was doing was wrong”.

During the four-day trial, the court heard from two psychiatrists, who had supported claims the woman was suffering from undiagnosed mental illness at the time of the incident.

“At the time of (committing the) profoundly violent acts against her sons the accused was suffering a disease of mind which led to a defect of reason,” Justice Button said.

In delivering the verdict, Justice Button said that although the woman “will not be held criminally responsible for her actions … there is no question that her actions directly caused the death of the younger boy and came very close to causing the death of the elder boy”.

The court heard the woman will be committed to the long term care of the Mental Health Review Tribunal in a specialist unit at the Mulawa Correctional Centre, Silverwater, in Sydney’s west.

“The tribunal must not release the accused into the community unless and until it’s satisfied the accused will not endanger (anyone else) or herself,” Justice Button said.

“I extend my condolences to all who have suffered and will suffer into the future including the accused herself who will come to see, if she hasn’t already, the enormity of what she has done.”

The boys’ estranged father lifted his hands above his head inside the courtroom and later lashed out over the decision calling the woman a “monster”, in a statement to news.com.au.

The man, who can’t be named, described her actions as “despicable and vile (acts) committed against my innocent children … which resulted in my son being (killed)”.

Shaking uncontrollably and teary, he told news.com.au he had been hoping the woman would be sentenced to 25 years’ jail for killing their youngest son and at least another 10 years for attempting to murder their eldest.

“Upon (the woman’s) release from prison and despite numerous threats she made to kill our children, (she) was released into the care of her mother, our childrens’ grandparent and guardian,” he said.

“Not only did this put my children in grave danger and at high risk, but also gave (their mother) every opportunity to plan and easily follow through with her premeditated resolve.

“(It was) the evil, twisted act of a monster.

“The only practical and fitting sentence for (her) should be a full life sentence.”

Wearing the same black pant suit for each day of the trial, the woman was this morning led into the dock by officers, where she took a deep breath and was told by her barrister to “breathe”. She turned around to family members in the public gallery and blew two kisses before sitting down. She appeared stony-faced when the verdict was read out.

In a video of his police interview played in court yesterday, the surviving boy gave a harrowing account of being nearly drowned by his mother and watching his five-year-old brother die when she turned on him.

The child, who told detectives his favourite cartoon character was the purple Ninja Turtle, Donatello, was just nine years old when he survived the horrific ordeal.

The bandaged child spoke to detectives from his hospital bed after the incident, and said his mother had lured the brothers to the river on the false pretence of going fishing.

Once the boys were in the water, their mother instructed the eldest boy to “put your head under”, he said.

“I just said ‘no’ … and then she dunked my head under the water. (I was) scared.

“My whole body (was under the water). My face was down.”

The boy said his mother “had her arm on my throat” and that he could feel the sand at the bottom of the river.

“Then I started hitting her so she would let go of me but she didn’t,” he said.

“I was starting to suffocate as she was hopping on me.

“(Eventually she released me) and then she grabbed my brother and did the same thing (to him). He couldn’t breathe also and then he died.”

The court heard the nine-year-old boy told police that when he made it to the bank he looked back at the river and saw his mother “shaking my brother” in the water. It was the last time he saw him alive.

In her police interview played in court on Tuesday, the woman described the horrific moment she forced the boys into a river, and held them under water.

The judge noted the woman had been crying, “bizarrely plaiting her hair” and “rocking back and forth” throughout the proceedings and so excused her from the court while police interview videos were played.

During her interview, the accused told detectives the day after the tragedy, that she had “blacked out and drowned her babies” because one of them “turned evil”.

The woman told police she first turned to her eldest son and “held his head under” the water.

“It was horrible,” she said in the video.

“He kept staying alive for a little bit. I had to sit on top of him. I couldn’t hold him down because he was so strong.”

The woman told detectives that at one stage she heard one of her sons scream: “Just stop, Mummy.”

The NSW Supreme Court heard the boy struggled for air before he eventually broke free.

“I didn’t want to keep doing it,” the accused said during her police interview.

“It was so f***in’ wrong.”

She then turned her sights to the younger boy, the court heard. In the video, she wailed as she told detectives she had one hand on her five-year-old son’s head and the other on his chest, while “holding him down”.

She said she could feel the little boy struggling, but didn’t relinquish her hold on him until he stopped, the court heard.

“I pushed him and let him float away so people would find him,” she said.

The child’s lifeless body was found in the river two days later following an extensive search by authorities.

In a statement tendered to court and viewed by news.com.au, the woman said she “caused the death of (her) child by drowning him” and that it “was (her) intention to kill” both of the boys when she took them into the river.

Earlier, the court heard that the woman was on supervised parole after having been released from prison, on aggravated break and enter offences, one month prior to the incident.

In his opening address, Crown Prosecutor Max Pincott said on the morning of the killing, the woman appeared angry and had called her mother from the Victorian town of Goornong and told her: “You won’t see us anymore.”

A few hours later, the accused took her sons to the riverbank and forced them underwater, the judge-alone trial heard.

A witness who heard screams ran to the river and saw the older boy being viciously 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 rescuer said in a statement. Another witness said in a statement that the surviving boy was “screaming and naked (and) covered in blood”.

“I started yelling out to my mum,” the boy said during his police interview played in court.

“I said ‘someone please help’.

“I tried to put my hands on the dog’s face so he wouldn’t do it but he was too strong.”

Another man saw the woman floating on her back in the river soon after. On Tuesday, the court heard the accused was trying to kill herself.

The nine-year-old was taken to hospital with life-threatening injuries and spent the next three days on a ventilator with aspiration pneumonia from the attempted drowning.

Later that night, local resort owner Michael Falzon saw the woman walking into his work premises soaking wet, bleeding and crying, at about 9pm.

Mr Pincott said 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,’” Mr Pincott said.

“When asked what she meant, she replied: ‘I had to drown my babies.’”

In a statement, Mr Falzon said the accused told him: “I just want a bullet, I should be dead.”

Mr 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,’” Mr Pincott told the judge.

The court heard that the woman told police: “I killed my kids … I didn’t want to do it. I am such a motherf***er.”

Mr Pincott said that when police asked where her kids were, she became upset and screamed: “I f***ing drowned them.”

The court heard she then referenced a former partner she hadn’t had contact with since 2016.

“F**k that c**t needs to be shot,” she said to officers, the court heard.

Defence barrister Eric Wilson SC said his client believed she was saving her children by killing them.

“She was keeping them safe, your honour,” he said.

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,” Mr Wilson said.

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

“She believes that she actually kept them safe.”

The judge said it was “thoroughly bizarre to think these acts were the solution to the problem”.

“One would know that being drowned is surely not (a pleasant death),” Justice Button said.

“It’s not as if the boys were given sleeping pills and simply drifted off to sleep.

“Being drowned would be a terrible way to die.”

Crown witness Dr Jonathon Adams, a forensic psychiatrist who assessed the accused murderer, told the court she appeared to have a borderline personality disorder and was likely suffering delusional beliefs at the time of the offence.

“I think she has borderline personality disorder, a longstanding substance abuse disorder and a likely major depressive disorder,” Dr Adams said.

“It appeared to me her mental state was deteriorating in the four weeks prior to the alleged offence.”

The court heard that the woman had a history of drug abuse but that toxicology reports showed she didn’t have any traces of illicit substances in her system at the time of her arrest.

Dr Adams said his patient had told him she used the drug ice once — to celebrate her birthday — in the four weeks between her release from jail and drowning her children.

She had also not been taking her prescribed antipsychotic medication since being released from prison in February, the judge was told. In the days leading up to the murder and attempted murder, the woman was seen screaming to herself: “You stupid sl*t”, “stupid b**ch” and “I’m going to kill him”. She was also caught shoplifting on two occasions during that time. The woman’s mother, who was caring for the boys, had taken an apprehended violence order (AVO) out on her daughter which banned her from coming near within 24 hours of consuming illicit drugs or alcohol.

The court heard that the accused had threatened “to drive with her and the boys into a tree” during a conversation with her mother in 2015. The incident was reported to police at the time.

The court heard the woman was subjected to physical, sexual and emotional abuse as a child and as an adult, and that she had a family history of schizophrenia.

Dr Adams said she had been “tormented” by voices in her head since the age of seven. In a report, he noted she had been self-harming since she was nine, first overdosed at age 13 and attempted suicide dozens of times. He said years of chronic substance abuse had worsened her condition and that she had most recently tried to starve herself behind bars.

megan.palin@news.com.au | @Megan_Palin