A father who believed he was saving the world by tossing his baby into the Tweed River has been found not guilty of murder on the grounds of mental illness.
Justice Helen Wilson returned her special verdict to the Supreme Court on Wednesday, saying the terrible tragedy was a result of the man "labouring under such a defect of reason" he did not know what he was doing was wrong.
The 49-year-old man's daughter was last seen "bundled and bobbing in the storm-tossed waters," floating out to sea by witnesses on November 17, 2018.
Her homeless father had previously tried to give his "cursed" baby away on numerous occasions to different acquaintances before he "sacrificed" her life "for the sake of this world".
"I would rather do time for you than let her walk," he later told police.
During his judge-alone trial the court heard he had been admitted to hospital at least 35 times over the years and had been a regular consumer of cannabis and alcohol, sometimes up to four litres a day.
He had expressed delusions of killing babies 17 years before he did so, often spoke about black magic and elders ruling his life, and "curiously" believed his girlfriend was Britney Spears.
Forensic psychiatrist David Greenberg on Tuesday said he was suffering chronic schizophrenia for some time and that he believed the killing was "justified" to prevent his daughter's first birthday and the "ending of the world".
The man's itinerant lifestyle and moving between states with the partner of his children had made it near impossible for mental health services to track his movements and adequately treat his symptoms.
He had not always been compliant with prescribed medication and had ceased his anti-psychotic dosages about two years before the killing.
Authorities had earlier filed concerns for the safety of his children but he belligerently refused any help offered to home the family.
After a "storm had brewed" on the border area that afternoon, the man - who was earlier observed aggressively yelling, pulling up pot plants and talking to a pole - left his partner and young son sheltered in the Tweed Mall car park.
He walked through torrential rain to rocks near the river where one witness saw him toss what they thought was a bundle of his objects into the water.
He then fell to his knees next to the river bank and lay facedown for several minutes before returning to his partner who asked where her daughter was.
"How dare you ask me things of god... I drowned her," he responded.
The family then travelled to Surfers Paradise by bus where currents and tides had also taken the baby girl 20 kilometres north to the Gold Coast beach.
Two days later a teenager made the grim discovery of her body while out for a midnight walk during schoolies.
Soon after her father was arrested and was later heard in a cell saying to himself he had destroyed "the most dangerous thing throughout the entire world".
While her cause of death was undetermined it was thought most likely to be drowning, or by suffocation after being held tightly under a blanket.
Justice Wilson concluded all expert evidence fell one way and that his mental health condition was made unquestionably worse by his abuse of alcohol and cannabis, but that it did not discount his "disease of mind" at the time.
She expressed her sympathies to the mother of the "happy and beautiful" baby girl whose life was taken from her.
He will remain detained in a mental health facility until he is deemed fit for release and not a threat to society or himself.
Australian Associated Press