In a Sydney courtroom on Monday, Aroha Hiroki begged to differ.

Taking the stand in the pair's joint Supreme Court murder trial on Monday, Aroha Hiroki laid the blame for Mr Katopodis' death firmly at the feet of her former lover and first cousin, who she claimed was an angry, violent drunk who regularly lost his temper and repeatedly abused her during their tumultuous relationship.

Aroha Hiroki told jurors Jason Hiroki used a beer bottle and one of his prized lawn bowls to hit Mr Katopodis on the head multiple times following a night of heavy drinking and cannabis smoking at their Gladstone Avenue home.

She described how earlier in the night Jason Hiroki had briefly knocked Mr Katopodis out when he caught him urinating all over the floor of the bathroom. She claimed her former lover lost his cool again that night, just moments after Mr Katopodis tried to drunkenly punch him and missed.

"He [Jason] pushed him against the wall and hit him again and Nick dropped," she said, adding she tried to calm Jason Hiroki down but he became aggressive towards her, prompting her to go outside for a few minutes.

Aroha Hiroki said when she returned, she saw Mr Katopodis lying on the floor of the dining room at Jason Hiroki's feet.

"Jason was [sitting on the dining chair] smoking a cigarette, he took a drink from his bottle, looked to Nick, then smashed the bottle over his head," Aroha Hiroki said, adding she told Jason Hiroki to stop. She claimed he then pushed her onto the floor of the kitchen before picking up a lawn bowl near his chair and again hitting Mr Katopodis in the head.

She told the court she retreated to the pair's bedroom, only to have Jason Hiroki ask her later to take responsibility for Mr Katopodis' death. "He asked me to take the blame," she said.

"I say 'no, I haven't done anything', but he said I could say it was self-defence and that Nick had tried to come on to me."

Aroha Hiroki claimed her cousin threatened to kill her if she went to police, and that she later helped him bury Mr Katopodis' body under their house because she was too scared of him to say no.

"He's tried to kill me [in the past]," Aroha Hiroki told the court, recalling an incident in which she said Jason Hiroki beat her up and tried to suffocate her, and claimed the assaults were so regular she considered them an everyday part of her life while they were together.

When asked why she hadn't told police "the truth" about Mr Katopodis' death during any of her three interviews with investigating officers, Aroha Hiroki said she had wanted to but had still been afraid of what Jason Hiroki might do to her, despite the fact he was behind bars on remand.

"But I want to do the right thing now, and I'm no longer under his control," she said.

Earlier in the day, Aroha Hiroki revealed her troubled upbringing in New Zealand, which included a traumatic incident in her childhood, severe alcohol abuse from the age of 10 and cannabis use from the age of 13.

She told the court she didn't progress past primary school, and by the time she was 14 was involved with a New Zealand gang called the Mongrel Mob.

She became the president's mistress at 16, then worked as a prostitute and pole dancer for the next few years until she and Jason Hiroki began dating and the pair moved to Australia.

She claimed she was involved in the sex industry in Australia as well at one stage in order to support what she said was Jason Hiroki's gambling addiction.

She named brothels in Unanderra and Wollongong as places she had worked.

The trial continues.