WARNING - DISTURBING CONTENT: A Sydney killer's bland and unemotional manner when detailing how she decapitated her mother is a symptom of her complex mental disorders, a psychiatrist has told a jury.
Jessica Camilleri – facing a murder trial over the kitchen killing in the family home in July 2019 – has no single diagnosis to explain her behaviour, forensic psychiatrist David Greenberg said.
He diagnosed her with a mild intellectual disability, autism spectrum disorder (ASD) that features a fixation on horror movies and figurines, and an intermittent explosive disorder (IED) that led to anger-based impulsive outbursts disproportionate to the provocation.
"When she reveals macabre details about how she killed her mother ... she doesn't use social gestures in the sense of communicating that," Professor Greenberg told the NSW Supreme Court jury on Friday.
"There's a bland lack of emotions on her face when she's discussing these difficult, emotional topics."
Killer can’t understand that ‘others have feelings’
Camilleri, 27, presented as ego-centric and failed to recognise that others also have feelings.
"Emotionally, (people with ASD) don't understand – they can't understand that it has that impact on another person," he said.
Camilleri told the psychiatrist she "saw red" when her mother threatened to call on emergency services to put her in a mental institution and was in a fit of rage when dragging her mother by her hair down the corridor.
Unlike her earlier accounts to police, she told the professor she reached for a knife first when she was in the kitchen.
Rita Camilleri's body was found on the kitchen floor near her eyeballs, tongue and tip of her nose, while the rest of her head was moved to the footpath outside by her daughter.
An autopsy found the 57-year-old was stabbed at least 100 times and had more than 30 defensive type wounds on each hand.
Camilleri has pleaded not guilty to murder – with the jury to decide if the charge can be reduced to manslaughter with the partial defence of being unable to control her actions due to a substantial impairment of the mind.
Psychiatrist says accused ‘explodes like a bomb’
Prof Greenberg found she likely had the capacity to tell right from wrong during the attack but her issues, particularly the IED, meant her capacity to control herself was substantially impaired.
"When she loses control, she explodes like a bomb," he said.
The IED wasn't "just the normal anger" most people experience and explained the frenzied nature of her attack "completely out of proportion of any stressor or provocation from her mother", he said.
Camilleri's fascination with horror movies violence could have resulted in her learning how to have "goal-directed and targeted aggression" and she may have "identified with these macabre acts to deal with disempowerment, low self-concept and poor sense of frustration tolerance".
Her low IQ meant she fell years behind at school, leading to incessant bullying and tormenting that played into her IED.
Females were always her victim – bar an incident when teachers were unable to get the then-15-year-old to release her bite on a boy – while she idealised men.
A "reasonable amount" of therapy over the years had resulted in very small incremental gains because of a deficiency due to her mental disorder.
"It's not just a lack of teaching – it's a lack of ability to integrate that into their repertoire," Prof Greenberg said.
She also had features or traits of ADHD, obsessive-compulsive disorder, depression and anxiety, and personality problems with narcissistic features.
Camilleri had poor relationships with her sister and father, and no friends.
"Her sole support and only real companion was her mother," Prof Greenberg said.
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