The new details, revealed for the first time on Friday, followed the triple murderer's failed bid to keep pre-trial evidence a secret to preserve her appeal rights.
Patterson, 50, initially faced three attempted murder charges over allegations from Simon Patterson she'd been trying to poison him since 2021.
The attempted murder charges were dropped by prosecutors after Justice Christopher Beale ruled Patterson should face them in a separate trial.
Simon revealed the nature of the allegations during pre-trial hearings in 2024, which had been suppressed until a judge ruled in favour of open justice.
"Open justice is a fundamental concern of our criminal justice jurisdiction," he told the Supreme Court in Melbourne.
Patterson pleaded not guilty to the attempted murder charges of Simon, as well as the three charges of murder and one of attempted murder.
Simon alleged Patterson had tried to poison him several times between 2021 and 2022.
The first was a penne pasta she cooked him before leaving for a camping trip in November 2021. Simon said he vomited and spent five days in hospital.
But the worst was allegedly after consuming a chicken korma curry Patterson made him, during a camping trip at Victoria's high country in late May 2022.
"While Erin was preparing food, I was getting the fire going, so I didn't watch her prepare it," Simon told a pre-trial hearing.
He began to feel unwell about midnight and was assessed at Mansfield Hospital the next day but discharged.
In the days after he got home, Simon's condition worsened and he ended up in a coma and underwent surgery to remove a large portion of his bowel.
In September 2022, he fell ill after eating a wrap Patterson prepared for him while they were camping together at Wilsons Promontory.
He went to his GP, Christopher Ford, about the alleged poisonings and then had Patterson removed as his medical power of attorney.
Dr Ford told a pre-trial hearing Simon was also apprehensive about eating cookies his daughter gave him, as he believed they might have been poisoned with antifreeze.
He went on an interstate holiday and Dr Ford said Patterson asked if he had eaten the cookies.
"He felt it was odd that she would be so focused asking about the cookies," Dr Ford told a pre-trial hearing.
Other pre-trial evidence released for the first time included documents about poisoning found on devices police seized from Patterson's home.
These included an appendix from a 2007 book titled Criminal Poisonings, which listed the colour, odour, taste and lethal dose of poisons.
Another piece of evidence, a Facebook post to a poisons page, was not shown to the jury.
"My cat chewed on this mushroom just now," the post said.
"He is having a vomit. Was in grassland near trees, I'm in Victoria Australia."
None of this information has been proven or tested before a jury because it was ruled out of the triple murder trial.
Patterson was found guilty by a jury of the murder of Simon's parents, Don and Gail, 70, and his aunt Heather Wilkinson, 66, along with the attempted murder of her husband Ian Wilkinson.
The jury found Patterson deliberately poisoned her four lunch guests in July 2023 by serving them death cap mushroom-laced beef Wellingtons.
Patterson will face a two-day pre-sentence hearing later in August, during which she will listen to statements from the Pattersons and Wilkinsons.
The plea hearing is on August 25 and 26.
Patterson will have 28 days to appeal after she is sentenced.
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