A 32-year-old aspiring doctor who fatally stabbed his father during a psychotic episode has been found not guilty by reason of insanity in the Supreme Court of Western Australia. Justice Terence Palmer delivered the verdict on Friday, concluding that David Nadi Lamie Moussa was deprived of the capacity to know that he ought not kill his father at the time of the attack.
The Incident
On February 4 last year, Moussa allegedly drove from Queensland to his father's home in Clarkson, armed with a 30-centimetre kitchen knife. He had been experiencing "dreams" of being abused, neglected, and drugged by his father as a child, and believed that "researchers" had ordered him to kill his father to end a "research project".
During his cross-country journey, Moussa was stopped by South Australian police for speeding at nearly 80 km/h over the limit. He claimed he was relocating to Perth and was low on fuel. Officers noticed the knife near the front passenger seat, but Moussa said it was used to cut duct tape for a broken bumper.
Upon arriving in Perth, Moussa camped at his father's home for several days until his father, stepmother, and six-year-old stepsister returned from a holiday in Thailand. He ushered his stepsister outside, saying he wanted to speak with his father and stepmother alone. He then allegedly pointed the knife at his father, stating: "I remember things from when I was young ... I never forget anything, I want to kill ... I am going to kill you both."
A scuffle broke out and spilled onto the driveway, where Moussa stabbed his father "six or seven times". His stepmother, Theresa Awad Soliman Salama, suffered lacerations to her abdomen and arm while trying to intervene. CCTV footage showed neighbours rushing to help the victim as Moussa calmly walked away and called triple-0, telling the operator: "I killed my father ... I stabbed him outside the house."
Mental Health Background
Moussa had been studying medicine at the University of Queensland and was diagnosed with ADHD, for which he took dexamphetamine. He also used medicinal marijuana for Crohn's disease. In 2025, he was placed on a mental health plan after telling a psychiatrist about "dreams" of his father abusing and neglecting him. He claimed his father drugged him and molested him as a child.
Psychiatrist Dr Adam Brett testified that Moussa suffered from schizophrenia and ADHD, and had developed psychosis before the offences. He said medication and stress led to delusional beliefs, including that his father would kill him if he did not act first.
Verdict
Justice Palmer noted that Moussa intended to kill his father, but his actions were driven by delusions from psychosis. "I am satisfied that David lacked the capacity to control his actions at the relevant time," the judge said. He added that Moussa's attack was premeditated and planned, but the intention was the result of a delusion.
Justice Palmer expressed no doubt that Moussa was remorseful, stating that "he and his entire family will be haunted by the tragic events of that day for the rest of their lives." He will now decide whether Moussa can be released under a community supervision order.
Community Reaction
Members of Perth's Arabic Christian Church community remembered Nadi Moussa, the victim, as a well-respected church leader who loved his family and faith. A churchgoer recalled that at prayer meetings, Nadi often requested prayers for his son David. Pastor Youssef Mikhail said it was comforting knowing that "brother Nadi" was now "with the Lord", but added that the church was shocked by the tragedy.
