Union boss John Setka's estranged wife threatened to kill him in "out of the blue" comments to a private investigator when she was at the end of her tether, a magistrate has found.
Magistrate Leon Fluxman on Friday found Emma Walters guilty of making a threat to kill Mr Setka.
She was captured in a recording from March 21 telling private investigator Adrian Peeters: "I have to kill my children's father to survive ... you're going to help me work out how I do it".
The comments were revealed in a secret video played to Melbourne Magistrates Court, which Mr Peeters said he was prompted to start recording by Walters having also made the threat earlier.
"She out of the blue … uttered that she needed a piece," Mr Fluxman said on Friday.
The magistrate rejected Walters' assertions that she was talking to Mr Peeters as a friend and using "florid" language out of frustration.
Rather, the pair had only spoken over the phone to organise a debugging job and she made it "absolutely plain that she had reached the end of her tether … and this was her last option".
Her claim she was pushing the private investigator for a quote was "simply not credible", contrary to Mr Peeters' powerful evidence he'd never heard anything like their conversation in his 23 years in the role, the magistrate said.
"It is clear that Mr Peeters was very alarmed by what you were saying, (and) that your utterances were ongoing and repetitive," Mr Fluxman said.
But the magistrate accepted Walters was a victim of "serious and sustained" family violence, and was at the end of her tether and desperate when she made the threat.
She also feared sexual violence at the time, the court was told.
Walters, 47, shared two children with the Construction, Forestry, Maritime, Mining and Energy Union's Victorian secretary.
The pair have been involved in a long-running legal battle involving allegations Setka committed acts of domestic violence, which he has denied.
Mr Fluxman found Walters was at least reckless as to whether Mr Peeters would fear she would carry out the threat.
She had faced an additional charge of attempting to commit an indictable offence over police claims she tried to acquire a handgun, but the magistrate dismissed that charge.
Mr Peeters previously told the court he began recording on his phone after about 10 minutes for his own safety after she told him she wanted to "lure" Mr Setka to the home.
"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 is heard telling Mr Peeters in the video.
She is also 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".
Walters told police she didn't want to kill Mr Setka but had to protect herself.
After leaving the property, Mr Peeters said he contacted Mr Setka, through the union, to warn him.
He then reported the incident to police.
Mr Fluxman decided against convicting Walters on Friday after her lawyer argued her financial means were "not great" and said a conviction could jeopardise her getting back into law, where she wanted to work with refugees seeking asylum.
He fined her $1500 and urged her to focus on herself, her children, her work prospects and her education as she completed a masters in migration studies.
"(The court process you've been through) will give you insight into the power of words and the effect that they can have on people," Mr Fluxman told Walters.
She declined to comment to waiting media outside court.
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