A Sydney mother who was allegedly decapitated by her daughter was "at her wits' end" and didn't know how to control her, a jury has heard.
WARNING: This story contains graphic content that some readers may find upsetting.
Jessica Camilleri, 27, is on trial for the murder of her mother Rita, 57, at their Western Sydney home last July and has pleaded not guilty.
The jury on Thursday heard of Ms Camilleri's tendency to make relentless prank phone calls to strangers, which often included threats of extreme violence.
She targeted employees of a Victorian business after finding mobile phone numbers online, the NSW Supreme Court was told.
According to its boss, Matthew Layfield, Rita Camilleri began to intervene after about two months and rang to apologise, advising she was trying to confiscate phones she found in her daughter's bedroom.
The calls, which numbered more than 100 a day and included threats to behead the recipient with a knife or chainsaw and "flush their head down the toilet" continued on and off for a year.
In a statement, Mr Layfield said he called Rita Camilleri and told her things were "getting out of hand" once his family members were also targeted.
Rita Camilleri replied by saying "I'm at my wit's end" and that she "did not know what to do to control her daughter", the court heard.
Mr Layfield said the calls would begin with Ms Camilleri apologising for calling so much and telling the recipient she was "not very well" and was trying to get help.
But the conversation would "turn ugly" when the target attempted to end the conversation, he said.
Camilleri told psychiatrist she was 'in a fit of rage'
Forensic psychiatrist David Greenberg described Ms Camilleri as "childlike", "naive" and "mildly anxious" during his two examinations of her.
"She was loquacious, over-inclusive and circumstantial in her thoughts," Professor Greenberg told the court.
Ms Camilleri gave an account of the night of the incident to the psychiatrist which contradicted what she told police, namely that her mother had not attacked her first.
She gave a detailed and gruesome description of her actions, and told Professor Greenberg she got the ideas from horror movies.
"I know people will think I'm sick," Ms Camilleri said, according to the psychiatrist's report.
"I thought, 'I'll put her out of her pain'."
Ms Camilleri told Professor Greenberg she was "in a fit of rage".
"I was so agitated and frustrated, because I was thinking sick thoughts."
The court has previously heard Rita Camilleri felt "let down" by psychiatrists and support services, and was "exhausted" from being her daughter's sole carer.
The officer in charge of the investigation, Detective Sergeant Grant Gilbert, said during a search of the family's St Clair home police found eight DVD copies of The Texas Chainsaw Massacre and five of Jeepers Creepers.
Ms Camilleri's legal team is arguing mental illness as a partial defence.
The jury has seen videos of Ms Camilleri speaking with police on the night of the incident, repeatedly claiming her mother attacked her first.
The trial, before justice Helen Wilson, continues.
