A Sydney man says his grandmother psychologically abused him before he snapped and stabbed her 40 times as a DVD of a trip the pair took to Hawaii played in the background.
Ethan Harwood pleaded guilty in April to the murder of Pauline Farrugia, 67, when he was aged 19 at her Penrith home in December 2017.
However, the now 21-year-old told a sentencing hearing in the NSW Supreme Court he didn't believe he was a violent person.
He said those around him constantly lied about why his mother had left him and his grandmother had always said her obligation to raise him "ruined her life".
"She would just say really horrible, nasty things," Harwood told the court on Friday.
"She would say 'I'm not blaming you, but the only reason why (your grandfather and I) separated was because I couldn't go out with (him) to the clubs ... you ruined my life. I can't go live in Malta because of you."
Harwood said he left his grandmother's house at 17 to live in rural Victoria but returned two years later, when he was again in Sydney and had been drinking heavily at a family barbecue.
He told the court he'd gone back because he wanted to know the truth after his mother told him Ms Farrugia had manipulated her into leaving him.
"I rang the doorbell and she let me in ... hugged me and kissed me on the cheek," he said.
"I wanted to piece together what's been said and to see if she really did make my mum leave me."
Later, after reminiscing about a past Hawaii holiday, he said the pair argued about why he had left the barbecue.
"She said 'I don't give a f***'. She started yelling at me for leaving - how could I do this to her, I'm so ungrateful, I'll never amount to anything, stuff like that," Harwood said.
"She was saying that mum turned me against her and she wouldn't let me go back with that woman."
Harwood said the words had made him feel "trapped" and he then stabbed his grandmother 40 times using two knives.
"I just thought I'm always going to be drawn between two sides, it's never going to end ... my world was caving in," he said.
Harwood didn't shed a tear as he recounted the moments leading up to the stabbing but said he felt "terrible" for his actions.
Asked if his grandmother deserved what had happened to her Harwood replied: "No, I don't think so".
Crown prosecutor Lou Lungo quizzed Harwood as to why he'd continued to lie to police and psychologists for 16 months after the attack, telling them he'd consumed drugs and had no memory of the killing.
Harwood said he was now trying to accept responsibility for what he had done.
Justice Michael Walton has reserved his sentence.
Australian Associated Press