Erin was angry because her husband filed taxes as a
separated spouse. Consequently, Erin no longer qualified for "married" tax deductions. She then started harassing her husband's family to coerce him into re-filing and falsely claiming that they were still married and living together. When they told her they were staying out of it, she decided to kill them.
After she swore at them on facebook, and after they knew that she may have poisoned her husband, they accepted an invitation to have lunch with her. They must have thought that, through kindness, she would stop being so angry.
The investigation was started only because her father-in-law brought some of his vomit to hospital and stated that he was probably poisoned.
"In late 2022, Simon told his GP, Dr Chris Ford (‘an old mate from church’) that he feared his wife had been trying to poison him. He also resolved to avoid unnecessary contact with her.
He then listed himself as single on his tax return. This move had significant implications for Erin’s financial affairs, since it stopped her claiming various tax breaks available to married people.
She responded by filing for child support, and the couple began arguing over money and who would pay their children’s school fees and medical bills. Efforts by Erin to persuade Simon's parents Don and Gail to intervene in this falling-out met with no success, and she subsequently fired off a series of hostile messages in a Facebook forum,
berating his extended family, saying (among other things) that she was ‘sick of this 


’ and ‘f*** em!’
In the spring of 2023, Simon began telling family members about his belief that Erin was trying to poison him. He confided initially in his 70-year-old father. But Don asked him not to share the concerns too widely because ‘he felt it could create issues in the way people related with Erin and our family’.
[...]
When all four guests then fell sick, the family immediately suspected foul play.
Indeed, Don was so convinced that Erin had sabotaged the lunch, he
turned up at hospital carrying a container filled with his own vomit, saying it ought to be handed to police ‘because he presumed this could be significant evidence because he thought it could be a deliberate poisoning’.
That, we can now reveal,
was the context in which the homicide squad first began investigating Erin Patterson."
In the end, Erin Trudi Patterson's fate was sealed by her lies. She lied about deliberately picking death cap mushrooms. She lied about buying and using a Sunbeam food dehydrator...
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