Rebecca Mossman Riley, facing a judge-alone trial on NSW's Central Coast, claims she was suffering dissociative amnesia during the attack and did not know what she was doing was wrong.
Mossman Riley has pleaded not guilty in Gosford District Court to two counts of wounding with intent to cause grievous bodily harm and one of common assault, denying she intended to hurt the couple.
Psychiatrist Olav Nielssen told the court Mossman Riley had been in a short relationship with her ex-boyfriend before he stopped returning calls.
Dr Nielssen said it appeared Mossman Riley, a binge drinker from an early age, had been drinking heavily when she confronted the man at Wyong Leagues Club, assaulted him and then claimed to have had no memory of the stabbing.
He said Mossman Riley told him she remembered initially confronting the couple, but claimed the next thing she remembered was heading to the bus stop and "I started feeling waves of emotion, feeling sad, betrayal, anger, and then nothing".
Questioned by prosecutor Liam Shaw on Tuesday, Dr Nielssen said despite Mossman Riley amnesia claims, she appeared to have been aware of what she was doing because "she picked the right bloke".
"She didn't stab a complete stranger and she stabbed his new companion," the psychiatrist said.
"She was aware of who it was she was stabbing. She didn't use a fork."
Police claimed Mossman Riley bumped into her ex-boyfriend and his new girlfriend at the club on January 7, 2023, and began arguing before being asked to leave about 9.30pm.The fight escalated in the car park before Mossman Riley stabbed her 29-year-old former boyfriend three times in the back and his new girlfriend, 31, once in the arm.
Mossman Riley then left as shocked onlookers helped the victims until paramedics arrived and took them to hospital in Newcastle.
Dr Nielssen said Mossman Riley, previously diagnosed with post traumatic stress disorder and borderline personality disorder, had "a degree of awareness" of what she was doing.
In his report, Dr Nielssen said: "Moreover, she did not have a condition that would typically deprive her of the awareness that stabbing another person was wrong. For example, a delusional belief."
Mr Shaw told judge David Wilson the Crown accepted Mossman Riley was mentally impaired on the night she attacked the couple but the issue was to what extent.
Defence barrister Alissa Moen said the judge would have to decide if Mossman Riley had specifically intended to stab the victims.
Symptoms of dissociative amnesia may include an individual experiencing significant memory loss related to a traumatic or stressful event.
Cross-examined by Ms Moen, Dr Nielssen said the new girlfriend's attitude of not caring about the situation would have inflamed Mossman Riley, given her various mental health issues.
"It's a dismissal, isn't it," the psychiatrist said.
"I imagine that would be more provocative to a person with her constellation of symptoms than other people."
The trial resumes on Wednesday.
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