Adelaide man thought his mum was an alien in a series of horrific attacks

Her son, who was aged 33 at the time of the incident, has been found not guilty of attempted murder by reason of mental incompetence. Photo / 123rf

WARNING: Confronting

An Adelaide man unleashed a series of horrific attacks on his mother, including dousing her in petrol and pushing her head into a freezer, because he believed she was an alien, a court has ruled.

The assault, which took place over several hours in October 2018, left the woman with life-threatening injuries that required treatment in a hospital intensive care unit for two months.

In what a psychiatrist described as a "sexual component to the attack", the woman also had her lung punctured with a wooden broomstick and required reconstructive surgery to her pelvis.

Her son, who was aged 33 at the time of the incident, has been found not guilty of attempted murder by reason of mental incompetence, news.com.au reported.

Justice David Lovell ruled he suffered from schizophrenia and was in the midst of a psychotic relapse at the time of the incident.

The court has ordered that the identities of the mother and son must be kept secret because of the nature of her injuries.

A judgment published by the Supreme Court revealed the man and his 59-year-old mother were alone at her southern suburbs home when she went to remove a loaf of bread from a freezer in the garage.

The man grabbed her from behind and tried to push her head down into the freezer, but she managed to fight him off.

He punched her in the face a number of times, grabbed a jerry can of fuel and followed her inside and around the home.

Later in the morning, he used the jerry can to throw fuel "over her and into her face".

The woman lost consciousness at that point and does not remember anything further about the attack.

Throughout the ordeal, she recalled her son "behaving like he was in a trance" and "his eyes being empty".

He told her she was "an alien who had his family" and asked "what did you do with my mum?"

Her husband, the father of the attacker, arrived home about 90 minutes later and discovered her lying unconscious on the floor of the ensuite bathroom.

She had been gagged with toilet paper, had bruises on her face and body, and had blood around her and on her clothing.

Her face and neck had been wrapped in electrical tape.

The woman was rushed to hospital for treatment, while the man was found at a yacht club, arrested and taken to hospital for a mental health assessment.

A psychiatrist who assessed the man said he remained convinced for weeks after the assault that his mother was shape-shifting creature.

The psychiatrist found he was suffering a psychotic relapse after he failed to take prescribed medication.

"The severity of his psychosis would have rendered him unable to reason about the wrongfulness of his actions," he said.

Justice Lovell accepted the report and found that the man did not know that his actions were wrong because he was mentally incompetent at the time.

He will now be subject to a limiting term, which he will serve under mental health supervision.

The man will reappear before the Supreme Court in October, before Justice Lovell sets the term.