Colin Mandy SC is expected to finish his closing address on Thursday after two days of arguing Patterson is innocent of three counts of murder and one count of attempted murder.
Prosecutors allege Patterson, 50, intentionally poisoned her former in-laws Don and Gail Patterson, Gail's sister Heather and Heather's husband Ian Wilkinson.
Don, Gail and Heather all died after consuming the beef Wellington lunch on July 29, 2023 served by Patterson at her home in regional Victoria, while Ian survived.
Mr Mandy argued that while Patterson told lies before and after the lunch, that did not mean she was guilty of murder and she had no motive to kill any of her guests.
He accepted her lie about having cancer was stupid but said she made it up to conceal her plans to undergo weight-loss procedures.
Mr Mandy denied the cancer lie was a ruse to bring the guests into her home, as she told the lie at the end of the meal once the beef Wellingtons had been eaten.
The barrister told the jury his client also ate the poisoned meal but her younger age, heavier weight and decision to throw up afterwards meant her symptoms were less severe.
Mr Mandy pointed to scientific research from Germany, which showed people could respond differently when consuming death cap mushrooms.
The defence barrister criticised prosecution claims that Patterson saw posts about death cap locations in the Gippsland area and then went to those places to forage for the mushrooms.
Mr Mandy told the jury there was no evidence Patterson saw the iNaturalist posts from April and May 2023 and cell tower data only suggested she might have been near Outtrim and Loch on the relevant days.
Once Mr Mandy finishes his closing address, Justice Christopher Beale will give his final directions to the jury.
The judge has indicated he will not begin his instructions until Monday, with the jury to start deliberating on Tuesday afternoon at the earliest.
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