Mushroom cook Erin Patterson is not on trial for lying and jurors should not find her guilty of triple murder based on her falsehoods, her barrister has argued.
Colin Mandy SC on Wednesday advised the Victorian Supreme Court jury to consider the evidence logically and rationally as he entered the second day of his closing address.
He pointed to the lie Patterson told her lunch guests about having a cancerous lump on her elbow, saying jurors should not jump from that deception to finding her guilty of murder.
"She's not on trial for lying," Mr Mandy said.
"This is not a court of moral judgment."
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 July 29, 2023 beef Wellington lunch served by Patterson at her home in regional Victoria, while Ian survived.
She has pleaded not guilty to three charges of murder and one count of attempted murder.
Prosecutors alleged Patterson made up the cancer claim so there would be a reason to have her guests over for lunch.
But Mr Mandy argued that proposition was "illogical and irrational" as the guests were only told the lie after the beef Wellingtons were eaten.
"If this was a ruse, there was no need to have the conversation because the deed - on the crown case, the consumption of the food - had already happened," he said.
"There was absolutely no need for Erin to say anything about cancer if that was a ruse."
The defence barrister conceded it was a "stupid" lie, but it was made because Patterson was embarrassed about her plans to undergo weight-loss procedures.
Although she never had any surgery, Mr Mandy told the jury Patterson did have an appointment scheduled with a clinic that performed liposuction.
He also raised the issue of an argument Patterson had in December 2022 with her ex-husband Simon over child support and the comments she made to Facebook friends about her in-laws.
In those messages, Patterson stated "this family, I swear to f***ing God" and "I'm sick of this shit, I want nothing to do with them".
Mr Mandy said she regretted using the words, but the tension was an aberration from her usual interactions with her in-laws.
The resounding evidence was that Patterson had a close and supportive relationship with Don and Gail, the court heard.
"In three short days, Erin made a handful of comments in the context of being hurt and frustrated ... and that's it," he said.
Mr Mandy encouraged the jury not to consider the evidence through hindsight, saying that could lead to irrelevant speculation.
"It doesn't matter what you may have done in a similar situation," he said.
The trial continues.
