The doting mother first killed the family's pet duck, then turned on the children - four boys and four girls, aged between two and 14 years. Quickly realising what she had done, Thaiday stabbed herself 35 times and waited to die on the front veranda where she was found by her adult son Lewis Warria, who called triple-0.
Thaiday, also known as Mersane Warria, was charged with eight counts of murder but will never stand trial after the Mental Health Court last month found she was of "unsound mind" at the time of the massacre.
Justice Jean Dalton said there was a convincing body of evidence that Thaiday suffered a psychotic episode and had no capacity to control or understand her own actions.
"To her way of thinking at that time what she was doing was the best thing she could do for her children, she was trying to save them," Justice Dalton said. The court heard Thaiday remained in a state of psychosis until July 2015 despite attempts to alleviate her symptoms with several anti-psychotic medications.
She has since relapsed twice, once at the two-year anniversary of the murders, and expressed the desire to kill other patients in the high-security facility where she is being held.
Psychiatrist Frank Varghese said Thaiday's illness was "schizophrenia at its very depth and at its worst".
Flowers at a memorial near the scene of murder at Manoora. Photo / AAP
"This is quite a unique case and a horrendous case, the likes of which I've never seen before," Dr Varghese told the court.
Several psychiatrists agreed Thaiday's persistent, lifelong abuse of cannabis triggered her schizophrenia, despite the illness usually manifesting in the younger years of life.
Thaiday did give up drugs and alcohol as part of her obsession with cleansing but by then it was too late, the symptoms had acquired "a life of their own". The court heard Thaiday had no criminal history and had not been in contact with psychiatric services despite previous disturbing episodes.
Justice Dalton ordered Thaiday continue to receive involuntary treatment and be allowed escorted leave on the hospital's grounds.
Local residents line the road as a hearse carrying one of the coffins of eight children drives by Murray street in the suburb of Manoora. Photo / AAP
She said she was impressed that Thaiday had acknowledged what she'd done and appreciated her rehabilitation was being hindered by grief and post-traumatic stress disorder.
"Her children were the things that had given her the most happiness in life," Justice Dalton said.
The Mental Health Act prohibited Justice Dalton's decision, made on April 6, from being published for 28 days.
