A Sydney woman who chopped her mum's head off with knives has been found guilty of manslaughter over the gruesome decapitation.

Jessica Camilleri, now 27, had pleaded not guilty by way of mental impairment to murdering her mother Rita, 57, in the kitchen of their St Clair home after a heated argument in July last year.

After two days of deliberating a NSW Supreme Court jury on Thursday returned the verdict of guilty of manslaughter instead of murder.

Jessica Camilleri has been found not guilty of murder.
Jessica Camilleri has been found not guilty of murder.

The five-day trial was told Mrs Camilleri had said to her daughter: "I've had a gutful of you" before a violent physical confrontation erupted involving knives late on a Saturday night.

"(Camilleri) said she grabbed about three knives altogether, two of which broke in the struggle," Crown prosecutor Tony McCarthy said.

"She estimated that she had stabbed her mother about 85 times and everywhere on her hands, arms, eyes, nose, she said (her mother) finally released her grip on her hair when she had been killed.

"She told police that in the struggle (her) head came off and it was only then that she stopped stabbing her. She said her eyeballs then popped out of her head, her tongue came out of her mouth and her nose came off."

After the attack Camilleri walked onto the street wearing a bloody nightdress and approached her neighbours, who phoned triple-0.

Senior Constable Anthony Digostino (and Senior Constable Jodie Reynolds after giving evidence at Darlinghurst Court.
Senior Constable Anthony Digostino (and Senior Constable Jodie Reynolds after giving evidence at Darlinghurst Court.

In body-worn video footage taken by Senior Constable Anthony D'agostino and played to the court, Camilleri pointed out where her mother's head was outside the home before asking repeatedly if anyone could bring her back to life.

"Listen officer, I know I've asked this like 20 million times now, I'm going to ask you one more time: there's nothing you can do, she's a goner, isn't she?" Camilleri asked.

Sen-Constable D'agostino replied: "She's deceased unfortunately, yes".

When Camilleri asked "they can't restart her heart or anything?", the police officer said: "No, not without her head unfortunately, they can't."

Camilleri then said: "I know doctors can do miracles, they can't sew her head back?" After a short pause, Sen-Constable D'agostino said: "That's a bit of a stretch".

Rita’s mother Rita Camilleri.
Rita’s mother Rita Camilleri.

Officers then found Rita's decapitated body lying face down between a cutlery drawer and a pantry in the family home's kitchen.

Underneath her neck were two intact eyeballs, to the right of her leg was a human tongue and near the fridge was the tip of a nose.

Camilleri later told a forensic psychiatrist she bit off her mother's nose and said she got the idea to cut off her head from horror movies, the court heard.

It wasn't disputed in the trial Camilleri killed her mum, but her lawyers wanted the jury to return a verdict of guilty of manslaughter instead of murder due to her mental state at the time.

The court heard she was previously diagnosed with a range of conditions, including an intellectual disability, an autism disorder and ADHD.

However, she didn't like the way her medication made her feel and was nervous about being placed into a mental facility.

Mrs Camilleri also had no recourse when her daughter refused to take her medication, the jury was told.

Defence barrister Nathan Steel told the jury in his closing address that Camilleri's attack on her mother was not premeditated and that it was a spontaneous anger-based response to multiple stressors.

The court was told Mrs Camilleri wanting to ring triple-0 to get someone to take her daughter away for the night had been an immediate trigger to her daughter.

Camilleri told officers in an interview she couldn't remember what she and her mother had started arguing over but that it was over something "petty".

"It was about these guys that I'm obsessed about that I've been harassing in the past," she said.

Judge Helen Wilson adjourned the matter and will sentence Camilleri at a later date.

Originally published as Manslaughter verdict after chopping mum's head off