A teenager was "acting on paranoid delusions" when he killed a fellow mental health inpatient, believing the victim was going to "assassinate" him.
In November 2022, Dusko Culibrk, 38, was killed in the adult mental health unit at Canberra Hospital.
On Tuesday, Aleu Mapiou was found not guilty by reason of mental impairment to one count of murder, and preventing the carrying out of a forensic procedure.
That means Mapiou will be kept in a secure mental health facility and will not be released until treating doctors believe he no longer poses a danger.
Even after his release, he may be subject to a psychiatric treatment order requiring he be medicated for his diagnosed schizophrenia.
In the ACT Supreme Court, Justice Belinda Baker handed down an indicative sentence of 20 years.
This reflected the potential jail sentence if Mapiou was found guilty, and will help decide how long a tribunal will keep the killer detained.
The special verdict of not guilty by reason of mental impairment was consented to by the prosecution, enabling the court to proceed without a trial.
However, Justice Baker was still required to independently evaluate the case.
Justice Baker found Mapiou, who was 18 at the time of the death, intended to kill Mr Culibrk and "did not appreciate his conduct was wrong".
She said the attacker was suffering a psychotic episode, due to his schizophrenia, which "caused him to lose touch with reality".
"[Mapiou was] acting on paranoid delusions ... [which] led the accused to form the belief the victim was intending to kill him imminently," Justice Baker stated.
The 18-year-old believed fatally assaulting Mr Culibrk was the only "way he could prevent himself from being assassinated by the victim".
"There is no suggestion these fears were based on anything the victim had done."
Mr Culibrk's mother previously described her son as "very generous" and said his family was "completely destroyed" by his death.
The killing
Court documents states Mapiou killed Mr Culibrk in November 2022 after about 11pm.
The day before a family member contacted police saying Mapiou was paranoid, delusional and they were concerned he was a safety risk.
Another family member told officers Mapiou had been "acting deranged", pacing back and forth holding a knife, and saying "we are all going to die and nothing matters".
He was placed under emergency apprehension in the mental health hospital.
On the day of the killing, Mapiou and the victim went missing and a nurse found them in Mr Culibrk's room with the door closed.
Upon tapping her swipe card to unblur a switchable glass panel, the nurse saw Mapiou with his back to the door carrying the other man.
Mr Culibrk was slumped on the floor, his head on the side of the bed and blood pooled nearby.
After trying to resuscitate the victim for almost an hour, medical staff pronounced him dead at 12.21am.
After his arrest, Mapiou rubbed moisturiser into his hands before police were able to take forensic swabs.
A forensic pathologist found Mr Culibrk's cause of death was "multiple blunt force head and neck injuries with a likely asphyxia component".
Mapiou's case has been sent for urgent review to the ACT Civil and Administrative Tribunal.
- Support is available for those who may be distressed. Phone Lifeline 13 11 14; MensLine 1300 789 978; beyondblue 1300 224 636.
