A mother has been cleared of poisoning her young son with faeces after enduring a six-year legal ordeal sparked by a single doctor's suspicions.
The 39-year-old Blue Mountains woman will now try to regain shared custody of her four children, who were removed from her care amid the accusation.
"I just want my children to know that Mum's not a bad person," the woman told AAP after the District Court of NSW found her not guilty on Tuesday. "I just want to get them back."
Paediatrician David Isaacs raised concerns the mother had injected her son with faecal matter in 2014, after a blood sample tested positive for e.coli and another bacterium found in the bowel.
The boy, then nine years old, had been admitted to Westmead Children's Hospital for asthma but then developed symptoms suggesting a bacterial infection.
Nurses overheard the boy say "Mum, what are you trying to put in my cannula?" when one of them was checking the drip three days before the sample was taken.
The next day he was heard to scream "why are you doing this, poisoning me?" when his mother was in the room.
Previous blood and urine samples were sterile.
Dr Isaacs thought it was highly likely the bacteria were deliberately introduced into the boy's bloodstream, and was worried the woman had factitious disorder, previously known as Munchausen syndrome.
As he was cross-examined at the week-long trial, he told the court he had previously missed a case of the disorder.
"If I get it wrong the child dies," he said in cross-examination.
"I have once in my life missed it and the child died and the mother told me afterwards what she had been doing with that child, and I'm never going to miss it again if I can help it."
Another expert witness, microbiologist Bernie Hudson, told the court the blood culture could have been contaminated in the lab or when it was being taken.
In closing submissions on Friday, crown prosecutor Lou Lungo conceded the charge could not be proved beyond a reasonable doubt.
"Because of the tragic loss of that child's life many years ago, (Dr Isaacs) was super vigilant ... and perhaps Your Honour would find that that clouded his opinion," Mr Lungo said.
There was not enough evidence to prove that faecal matter had been injected into the boy, or that the mother did it, NSW District Court Judge Justin Smith ruled on Tuesday.
The son had been delirious and confused in hospital and repeatedly denied to police that his mother poisoned him.
The woman wept as the judge told her she was free to go.
"The only thing that was administered in this case has been a gross injustice to the accused for more than six-and-a-half years," the woman's defence barrister, Pauline David, said outside court.
"She has lost her children ...She has lost financially ... She has lost her ability to work in her occupation as nurse. And she has also nearly lost her sanity."
In a statement through her lawyer, the woman criticised Dr Isaacs for his accusation.
"Other obvious innocent explanations for the positive blood cultures were ignored and never investigated," she said.
The mother told AAP the "horrific" experience caused her to have a complete nervous breakdown and spend months in a mental health ward, where she underwent 20 courses of electro-convulsive therapy.
She no longer trusts doctors or hospitals.
She has only been able to have contact with her children in the last six months and had missed their formative years, she said.
"Now I just want to focus on being able to see my children," she said.