The estranged husband of death cap mushroom cook Erin Patterson has taken the stand as the first witness in her triple-murder trial.
The 50-year-old mother, who has pleaded not guilty to three murder charges and one of attempted murder, faced court in Morwell on Thursday, about 150km southeast of Melbourne, as the first witness was called.
Patterson had invited her husband Simon, from whom she separated in 2015, to the deadly beef Wellington lunch in July 2023 but he declined her invitation.
His parents Don and Gail Patterson, and his aunt and uncle Heather and Ian Wilkinson all went to the lunch at Patterson's Leongatha home.
Three of them died in the days after while the fourth, Ian Wilkinson, became very sick but survived.
Prosecutor Nanette Rogers SC told the jury on Wednesday that Simon Patterson had texted to say he felt "too uncomfortable" to attend the lunch the day before.
She said after their separation the pair remained amicable as they shared custody of their two children and would go on family holidays together.
"Despite their separation in 2015, Simon remained hopeful for some time that he and the accused would some day reunite," she told the jury of 15.
"They continued to communicate with one another and other members of the Patterson family via the Signal messaging application."
But she said Simon noticed a "sustained change" in his relationship with Patterson in 2022 after he listed himself as separated on his tax return.
Simon offered to amend his tax return but Patterson said she would need to see child support from him instead, which he accepted, Dr Rogers said.
"However, their communication from that point started to decline," she said.
"Issues arose concerning the payment of child support, including whether Simon should make additional payments outside of child support for expenses such as school fees."
Prosecutors claimed on Wednesday that Patterson told a series of lies before and after the fatal lunch on July 29, 2023.
These included false claims she had cancer, and lies to police about disposing of a dehydrator and that she did not go foraging for mushrooms.
Prosecutors also alleged she feigned illness after eating her portion of the lunch.
Defence barrister Colin Mandy SC said Patterson accepted some of the claims she lied, but denied not telling the truth about becoming sick after the lunch.
He claimed she told some lies because she had "panicked" after her guests became ill from her cooking, amid intense police and media scrutiny.
Patterson had no intention to kill or cause "any harm" to any of her guests, he said.
She invited the group to lunch at her home following Sunday service at Korumburra Baptist Church on July 16.
She served beef Wellington to her guests, which consisted of steak covered in a paste containing death cap mushrooms, wrapped in pastry.
Dr Rogers said Patterson served the meals to her guests on different plates to her own.
The trial before Justice Christopher Beale continues.
