Killing driven by delusions: court told

A MAN accused of bludgeoning his mother and step-father to death was convinced killing them was the only way to avoid readmission to a psychiatric unit, a jury has heard.

West Australian Nicolau Fransisco Soares has pleaded not guilty to murdering Dr Delys Weston and Professor Gavin Mooney in December 2012 on the grounds of insanity.

Forensic psychiatrist Michael Jordan told the Hobart Supreme Court Mr Soares had been living with schizophrenia since as early as 2006, with his condition characterised by grandiose delusions and paranoid beliefs.

Dr Jordan said the accused's mental health had deteriorated steadily since his symptoms were first identified.

Mr Soares had been admitted to psychiatric facilities three separate times, relapsing after each occasion after missing his medication.

Dr Jordan said at the time of the attacks the accused did not believe or accept he had a mental disorder, and was convinced the medication prescribed to him was poison.

The court heard Mr Soares believed he was destined to join elite ranks of the armed forces, determined to learn skills necessary to defend himself against a range of perceived threats and to survive what he thought would be an impending apocalypse.

The court heard before attacking his mother and step-father, Mr Soares overheard a conversation between the couple and a local pharmacist as they tried to obtain medication for his illness.

The court heard Mr Soares expected the couple might have him admitted to a mental institution, which be believed would prevent him joining the army.

"His overriding ambition and drive was to join the army and he was prepared to kill to make sure he could carry on that pathway," Dr Jordan said.

"He came to the conclusion the only way he could prevent his admission to the psychiatric unit was by killing his mother and step-father."

Dr Jordan said Mr Soares decided he had to "get the killing done", and resolved to carry out the attack as quickly as he possibly could.

The court heard the accused had been psychotic for many months, and that the killings were driven solely by his delusions.

"He'd reached such a crescendo that his ability to balance right from wrong had been lost," Dr Jordan said. "He had no appreciation he was unwell, and no understanding his mother and step-father were simply trying to do the best for him."

The trial continues today.