Michael Bracken turned to his son, Phillip, and said, "This crazy bitch is threatening to kill me" after an angry Helen Curtis had been abusing him outside his West Footscray home, a court has heard.

Phillip told his father "Don't worry Dad, you just go home," before he took a rifle from Ms Curtis's car and shot her dead in the middle of Clive Street.

Fork lift driver Phillip Bracken, 45, has pleaded not guilty in the Supreme Court to murdering Ms Curtis, 58, his de-facto wife of four years, on Monday afternoon, November 19, 2012.

He claims he killed Ms Curtis in self-defence after having been abused, controlled, threatened and intimidated by her.

Michael Bracken told the court Ms Curtis initially went overboard trying to impress him and his wife Sandra after meeting Phillip but "as she got to know us ... she pretty much forgot about being a nice person and started to develop into a nasty person".

"We were having verbal arguments that were instigated by herself because she couldn't quite cope with my conduct or mannerisms."

Asked what he meant, Mr Bracken replied: "Well, I had probably a bad habit of correcting her when she made stupid or untrue statements and she didn't like being corrected."

Mr Bracken said it was about a year before Ms Curtis, an unemployed truck driver, was shot dead when he told her she was no longer welcome in his home.

"She turned up to my home one Saturday evening with Phillip and immediately bore full throttle into myself as to what a rotten this and that and everything else I was, and she wasn't going to put up with it, and just went on and on and on about how she hated me and all the rest of it.

"I said, 'Well, that's fine by me, you know, just let's call it quits while we're ahead.'

"After that particular incident I told Phillip never to bring her near me again, I never wanted to see her as long as I live."

Mr Bracken claimed that six months earlier he had seen a confrontation between Phillip and Ms Curtis where she attempted to attack him with a chef's knife.

He later told her that people who run around with knives, trying to attack their partners, finish up in an asylum.

"She said: 'I couldn't give a shit what people think, or what they say, the little bastard's been cheating on me and I'm going to punish him for it'."

Mr Bracken said he later phoned Phillip who told him Ms Curtis was taking the drug Xanax and: "She's crazy Dad, but once she calms down, she'll be all right."

"That was a turning point in all of our relationships, and I said to Phillip: 'Look, if you don't get out of this relationship, she's going to finish up killing you or you'll both be killed.' And he said 'I know, Dad, but there's nothing I can do about it'."

Mr Bracken said that as soon as Ms Curtis found out he was trying to get Phillip to end the relationship, she turned on him and called him an "interfering old bastard".

He had not seen Ms Curtis for a year before she turned up outside his house on November 19, 2012, and began abusing and threatening him.

Mr Bracken told the jury that when Phillip arrived in Clive Street after receiving a phone call from Ms Curtis, he told his son, "This crazy bitch is threatening to kill me. Can you take her away, or take her home". Phillip replied: "Don't worry Dad, you just go home."

After shooting Ms Curtis, Phillip went back to his father and said, "Tell mum I love her, and I've done this for you and her."

The trial, before Justice Chris Maxwell, continues.