Her estranged husband Simon Patterson’s parents and aunt fell ill and died after they ate a beef wellington dish at Patterson’s home on July 29, 2023.

Don and Gail Patterson, both 70, and Gail’s sister Heather Wilkinson, 66, died in hospital in the weeks after the gathering.

Wilkinson’s husband, Korumburra Baptist Church pastor Ian Wilkinson, fell gravely ill but recovered.

Outlining the case against Patterson, Crown prosecutor Dr Nannette Rogers, SC, said the death cap mushroom poisonings of each of the lunch guests was initially thought to be a “mass food poisonings event”.

The jury was told Patterson and Simon met in the early 2000s while they both worked for the Monash city council.

They separated in 2015 but remained amicable, Rogers said.

Rogers said Patterson had allegedly invited her husband, his parents and his aunt and uncle for lunch after a service at the Korumburra Baptist Church to discuss a medical issue.

The jury were shown pictures of Patterson’s Leongatha home, where the lunch occurred, and a diagram outlining the Patterson and Wilkinson families.

Husband hoped to ‘reconcile’: Prosecution

Rogers said despite Patterson and Simon separating for the final time in 2015, they remained “friendly, amicable and affable” while continuing to co-parent.

“Simon remained hopeful that he and the accused would reconcile,” she said.

Rogers said Simon first noticed a “change” in Patterson’s demeanour in 2022 after he filed a tax return stating they were separated.

‘Cancer diagnosis’ the reason for lunch: Rogers

Rogers said Patterson had spoken to Simon’s parents in June 2023, saying she had a “lump in her elbow” and would be attending hospital on June 28.

“The day of her purported appointment Gail Patterson sent the accused a message asking how she had got on that day,” Rogers said.

She said Patterson allegedly responded it “went okay” – she’d had a biopsy but would need to return the following week for an MRI.

After a service at the Korumburra Baptist Church in July, Patterson invited Simon, his parents and his aunt and uncle around for lunch.

After her estranged husband said he would not attend because of being uncomfortable, Patterson allegedly sent him a message, the court was told. Rogers said Patterson allegedly said she was disappointed because “she wanted it to be a special lunch”.

“It was important for her that everyone attended the following day and she hoped to see him there,” Rogers said.

Rogers said after the lunch, Patterson told the guests she had cancer and asked for advice on how to tell her children.

What Erin Patterson allegedly served at lunch

Rogers told the jury the four lunch guests arrived on Saturday, July 29, and were shown around Patterson’s recently built Leongatha home.

She said Patterson allegedly served individually portioned beef wellington with mashed potatoes and gravy.

After the lunch, the prosecutor said they ate cake and a fruit platter provided by Wilkinson before leaving all together about 3pm.

Rogers said it was the Crown case that each of the four lunch guests began experiencing gastrointestinal illness about 12 hours later.

By midday the following day, each was in hospital, she said.

“Over the following days their conditions declined … despite receiving maximal care, Don Gail and Heather each passed away.

“Ian Wilkinson was the only lunch guest to survive.”

Alleged mushroom poisoner checked out of hospital against advice, jury told

Rogers told the jury Patterson self-presented to hospital at 8am on Monday, July 31 – two days after the lunch.

She said Patterson complained about gastrointestinal symptoms and was advised she had potentially ingested a lethal dose of death cap mushrooms.

“The accused repeatedly said she needed to leave … she was adamant that she would not stay,” the prosecutor said.

She left at 8.10am against medical advice, Rogers said.

The prosecutor told the court Leongatha Hospital’s Dr Chris Webster took the step of calling police for a welfare check and officers visited her home.

Patterson returned to the hospital at 9.45am, Rogers said.

Rogers said Patterson told staff her children had eaten the leftovers, with the mushrooms scraped off, but did not want to bring them to hospital.

“Is this really necessary? They don’t have symptoms,” Patterson allegedly said after Webster warned her it was “critically important”.

“I just don’t want them to be scared.”

Dried mushrooms came from Chinese grocer: Patterson

Rogers told the court Patterson was questioned on where the mushrooms from the lunch came from.

She allegedly said she purchased 500g of sliced button mushrooms from Woolworths and also used a packet of dried mushrooms purchased from a Chinese grocer in the Melbourne suburb of Oakleigh in April 2023.

Earlier, trial judge Justice Christopher Beale outlined the four elements of murder and the four elements of attempted murder the jury would have to be satisfied beyond reasonable doubt on if they were to convict Patterson on any of the charges.

For the charge of murder, these elements are that her conduct caused the death, was done consciously, deliberately and voluntarily, done so intending to kill or to cause really serious injury and had no lawful justification.

Ten men and five women were empanelled to serve on the jury for the estimated six-week trial on Tuesday.

The trial is being heard in the country Victorian town of Morwell, about 45 minutes from Patterson’s Leongatha home.

Her barrister, Colin Mandy, SC, is expected to deliver the defence response later on Wednesday, identifying any issues in dispute the jury will need to determine.

The trial continues.