Mushroom cook's co-parent relationship 'very negative'

The relationship between mushroom cook Erin Patterson and her estranged husband was "very negative" in the months before she served a deadly beef Wellington lunch, their teenage son told police.

Patterson's 14-year-old son described his parents' relationship in a recorded police interview played to the Victorian Supreme Court today in his mother's triple-murder trial.

Patterson is accused of murdering her former in-laws Don and Gail, and Gail's sister Heather, who all died after eating a beef Wellington laced with death cap mushrooms at Patterson's home.

Heather's husband Ian Wilkinson survived the July 29, 2023 lunch and Patterson has been charged with his attempted murder.

She has pleaded not guilty to all charges.

Patterson's son told police his mother moved houses about seven years before the deadly lunch after having a "couple of arguments" with his father Simon Patterson, although the couple did not divorce.

The original arrangement was for the children to stay with Erin during the week and Simon on the weekends but that changed in the year before the lunch, the boy told police.

He said his parents' relationship had become "very negative".

"I know dad does a lot of things to try and hurt mum, like messing around with the school," he said in his interview.

"Mum didn't put his name on the billing for the school ... but dad wouldn't talk to mum about that. He would just ring the school and tell them to put his name on the billing."

The boy told police he had been living solely at his mother's house in the past year, even though Simon was trying to convince him otherwise.

"I didn't want to," the teen said.

"He never did anything with us over the weekends when I did stay there."

The boy said his mother felt sick the day after the lunch so they did not go to church but she still wanted to take him to his flying lesson more than an hour's drive away.

The teen told police his mother did not need to pull over to use the bathroom during the drive there and back, although she rushed to the bathroom when they returned home.

The jury was told Patterson served her children the leftover steak, potatoes and beans from the lunch for their dinner on the Sunday night.

The boy said he usually did not like eating leftovers but this meal was different.

"[The steak] was very soft and it was probably some of the best meat I've had," he said.

The teen also ate the rest of his mother's meal as she was not feeling well enough to finish it, he said.

The jury was told while the boy did not love mushrooms because they were "squishy and mushy", he believed his mother did.

He recounted a time in mid-2020 when he and his mother found some wild mushrooms growing in the Korumburra Botanic Park.

"I remember mum took a picture of them because she thought they looked nice," the boy told police.

"It was just a very fond memory."

They did not pick the mushrooms and the boy said he had never been foraging for wild mushrooms with his mother.

Patterson's nine-year-old daughter also told police she had never searched for mushrooms with her mother or brother.

In her record of interview played to the court, the girl said Patterson was a "very good" cook and she enjoyed cooking.

She also described eating the leftovers, saying there was no gravy or other ingredients other than steak, mashed potatoes and beans.

The trial before Justice Christopher Beale in the regional town of Morwell will return on Tuesday.