The 50-year-old woman is nearing the end of a Supreme Court jury trial in regional Victoria, with the prosecution completing their evidence to a jury of 14 on Monday afternoon.
The prosecution's final witness was Detective Senior Constable Stephen Eppingstall, who spent about five days in the witness box.
"The crown formally closes its case," prosecution barrister Nanette Rogers SC told the jury.
About 3.15pm on Monday, defence barrister Colin Mandy SC told the jury he will call Patterson as a witness.
"Your Honour, the defence will call Erin Patterson," he said.
Her defence admitted Patterson told a number of lies at the beginning of the trial, including that she did not own a food dehydrator and had never foraged for mushrooms.
She has pleaded not guilty to three murders over the deaths of her estranged husband's family, after serving them a toxic beef Wellington at her Leongatha home on July 29, 2023.
Her former in-laws, Don and Gail Patterson, 70, and Gail's sister Heather Wilkinson, 66, died in hospital from death cap mushroom poisoning days after the lunch.
She is also charged with the attempted murder of Heather's husband Ian Wilkinson, who became sick but survived the meal.
Mr Wilkinson has sat inside court almost every day since he gave evidence in the second week of the trial, which is sitting at Latrobe Valley courts in Morwell, about two hours' drive from Melbourne.
Mr Mandy told the jury earlier the defence case was Patterson had "panicked" and told some lies "because she was overwhelmed by the fact that these four people had become so ill because of the food that she'd served to them".
The poisonings were unintentional, "a tragedy and a terrible accident", he said.
However, the prosecution claims Patterson deliberately poisoned her lunch guests.
The trial before Justice Christopher Beale continues.
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