Raina Thaiday killings Cairns Australia
A woman is comforted during a church service for eight children who were killed in the Cairns suburb of Manoora, 21 December 2014 REUTERS/Dan Peled/Pool

An Australian woman who slaughtered her own seven children and a niece in a psychotic episode will not face charges, it has been announced.

Raina Thaiday, from Cairns, killed the eight then stabbed herself 35 times at a property in Cairns on 21 December 2014. She has been detained at a high-security centre in Brisbane ever since.

Justice Jean Dalton of Queensland's Mental Health Court made the ruling last month (April) but it has only just been made public. Dalton said it was clear Thaiday - also known as Mersane Warria - was of unsound mind when she carried out the attack.

Although she had never been treated for mental illness, she had been a cannabis user for years and shortly before the killings was smoking up to 20 "cones" (conical joints) per day.

Thaiday reportedly gave up cannabis and alcohol before the killings and became obsessive about cleaning the house. Neighbours heard her talking to herself about killing her children in order to "save" them. The killings are thought to have been triggered by Thaiday hearing a dove call and believing it was a signal.

"She heard the sound of a bird and believed from hearing that sound it was a message she must kill the children to save them," forensic psychiatrist Dr Jane Phillips told the court. After slaughtering the family duck she killed her four sons, three daughters and one niece, aged from two to 14.

Thousands of people attended a funeral service for the eight children - Malili, Angelina, Shantae, Rayden, Azariah, Daniel, Rodney and Patrenella - including then-Prime Minister Tony Abbott. The house was later demolished and eight frangipani trees are being planted at the site as a memorial.

Condition has worsened

Thaiday's mental condition is said to have deteriorated since the killings and she has made threats to kill other residents at the centre. It is unclear if the 40-year-old will ever be released back into the community. Justice Dalton said Thaiday now understood what she had done and her rehabilitation was affected by her grief and post-traumatic stress.

"Ms Thaiday had a mental illness that deprived her of capacity at the time of the killing," said Justice Dalton. "That is, that she is entitled to the defence of unsoundness of mind - there is just no doubt about that on the evidence, and there is no doubt about the legal conclusion that flows from that."