Emma Walters, 47, who shares two children with Mr Setka, faced Melbourne Magistrates Court on Tuesday over allegations she threatened to kill the Victorian secretary of the Construction, Forestry, Mining and Energy Union, and tried to get a gun to carry out the murder plot.
Walters has pleaded not guilty to one charge of threatening to kill Mr Setka and another of attempting to commit an indictable offence.
Emma Walters was secretly recorded by a private investigator.
She was secretly recorded by private investigator Adrian Peeters after he visited her in March 2023 following a request from Walters about "debugging" her West Footscray home.
But Mr Peeters said the conversation "shifted quite quickly" away from debugging, to her alleged plot to kill Mr Setka.
"Ms Walters initiated the shift, she stated that she needed a 'piece' and she had to kill the father of her children," he told the court on Tuesday.
The video Mr Peeters recorded, taken on March 21, was shown to the court as Walters fights the criminal charges.
"I know how to use a gun alright, and I'm willing to deal with the consequences of having to go through the court process of self-defence," Walters can be heard telling Mr Peeters.
"I have to kill my children's father to survive, and that is not a very good position to be in.
"Anyway, you're going to help me work out how I do it."
She is then heard telling Mr Peeters she was a "lawyer by trade" and that "this conversation never happened... once it's in the court you cannot say that you have any knowledge of it".
Emma Walters told police she didn't want to kill John Setka but had to protect herself.
Mr Peeters alleged Walters told him "I need to lure him here", referring to Mr Setka, before he started the recording.
He said he recorded the conversation for his own safety, and after leaving Walters' property he contacted Mr Setka through the union to warn him.
He then reported the incident to police.
Walters was arrested on March 29, and her police interview - where she is shown the video recording - was also played to the court.
She told detectives she was frustrated, distressed and used "florid language" because she "had a responsibility" to protect herself and her children from Mr Setka.
"The police have failed to protect me and the children," she said, in the interview.
"Do I want to kill John Setka? No, not at all. Do I have to protect myself? Yes. Do intend to use a firearm to do so? No.
"That's a woman that's been in distress and the system has failed her and her children, time and time and time again, I was trying to express that."
The hearing before Magistrate Leon Fluxman continues.
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