Medical student drives from Queensland to Perth to stab elderly dad

David Moussa was studying to be a doctor when in January last year he felt compelled to drive from Queensland to Perth to stab his father to death.

The 32-year-old believed his dad had drugged, neglected and sexually abused him as a child and that he had been “told” to kill the 72-year-old by medical researchers, the Supreme Court of WA heard on Tuesday.

Moussa has gone on trial this week after pleading not guilty to the killing by reason of unsound mind. He entered the same plea in relation to a grievous bodily harm charge after he stabbed his step-mother during the same incident outside their Clarkson property on February 4 and 5 2025.

On Tuesday, the court heard how Moussa, who has a master’s degree in science from UWA, was living and studying in Queensland completing the first year of a medical degree when his physical and mental health began to decline.

He was falling behind at university and sought help from his GP and a psychiatrist who just weeks before killing his father wrote that Moussa was suffering from psychotic symptoms from dexamphetamine use.

He was also struggling with the end of a relationship, a failed rent inspection and had lost and then appealed his place at medical school because of failing grades, the court heard.

One of his medical case notes said he was experiencing “homicidal ideation” but that he “denies travelling to Perth to harm family”.

On January 22 last year Moussa filed an online police report alleging his father, Nadi Moussa, abused him as a child.

Five days later he got into his Mercedes and drove from one side of the country to another with a 30-centimetre Japanese cooking knife next to him.

When police in South Australia pulled him over for speeding, they saw the knife and a roll of duct tape in the foot well of the passenger seat and asked him about it. He said the knife was for cutting the tape that he was using to stick on his rear bumper that was hanging off after he hit a kangaroo.

They believed him and let him go.

Days later, after lying in wait at their Clarkson home while they holidayed in Thailand, Moussa lured his six-year-old half sister out of the house lying that he had “lollies” for her and then proceeded to stab his father to death.

The 72-year-old stumbled out of the house and onto the driveway.

Nadi Moussa’s wife, 52, tried to intervene and was stabbed in the process, but survived her injuries.

The court heard Moussa told the couple “I need you to sit down here, I want to kill you both, sit down here”.

After the killing, Moussa then calmly called triple-zero, the chilling phone call played to the court on Tuesday where he can be heard telling the operator that his dad was dead.

He later told police he stabbed him quickly because he didn’t want him to suffer and said that he told him that he was sorry. He told the operator he had stabbed him 50 times in the heart.

A psychiatrist assessed Moussa after his arrest and he was separately treated for schizophrenia. He was described as being “acutely unwell at the time of the offences”.

Moussa’s two brothers denied their father was a paedophile and said they had a loving and happy childhood.

In a recorded police interview taken on the day of the incident that was played in front of Moussa’s judge alone trial, he can be seen calmly telling the interviewing officers that he had driven to Perth with the intention of killing his father.

The officers asked him why he did it.

“I don’t know, my eyes were closed at the time,” he says. “These researchers come to see me about twice a year. They told me it was their hope that I would do it because if they did it, they would get in trouble if they did it. They wanted me to do it so it would end the research they were doing on me.”

Moussa was held at Frankland Centre after his arrest before being transferred to prison.

The trial has now concluded and the verdict has been reserved until later this week.