Mushroom lunch leftovers examined and a juror removed: how week three of the Erin Patterson murder trial unfolded

The mushroom paste was contained in a vial about 2cm wide and 5cm high, with the exhibit name EX X1 Z13.

The paste was taken from inside a beef wellington, which in turn was taken from inside a paper bag found in a wheelie bin outside Erin Patterson’s home.

Unlike other forensic samples of paste taken from the same location, this one contained traces of an amatoxin found in death cap mushrooms.

As was made clear on the first day of Patterson’s triple murder trial, there is no dispute that the beef wellingtons she made for her lunch guests on 29 July 2023 contained these mushrooms. What is in question was whether she meant to use them, and, if she did, what her intention was when she did so.

Patterson, 50, has pleaded not guilty to three charges of murder and one charge of attempted murder relating to the lunch she served at her house in Leongatha, Victoria, about 135km south-east of Melbourne.

She is accused of murdering her estranged husband Simon’s parents, Don and Gail Patterson, and his aunt Heather Wilkinson. She is also accused of attempting to murder Ian Wilkinson – Simon’s uncle and Heather’s husband.

The Victorian supreme court sitting in nearby Morwell has previously heard the guests died after being poisoned with death cap mushrooms. The prosecution alleges Patterson deliberately poisoned her lunch guests with “murderous intent”, but her lawyers say the poisoning was accidental.

Shortly before giving evidence about EX X1 Z13 this week, Dr Dimitri Gerostamoulos, the head of forensic science and chief toxicologist at the Victorian Institute of Forensic Medicine, was asked by prosecutor Sarah Lenthall what the estimated lethal dose of amatoxins was for humans.

He said it was a very small amount.

“Just to complete the mathematics there. For a 70 kilogram adult?” Lenthall asked.

“It’s about 50 grams, or three tablespoons, if we can put it in common terms,” Gerostamoulos said. “But it will depend on how much of the toxins are there, the species of the particular plant.

“These estimates are derived from studies that have been conducted in mice, rats and dogs. They’re not studies that have been directly derived from humans, for obvious reasons, but they are very toxic compounds.”

Gerostamoulos also gave evidence about a 2017 German study that included a table outlining the severity of amatoxin poisoning, from grade 1, being least severe, to grade 4. The study noted that “other persons who have eaten the same meal may develop higher severity grade” symptoms.

He went on to say the factors which could influence this included the amount the person had eaten, their weight, their general health and their toxic response.

When asked directly by Lenthall what he expected the outcome would be in a case where two people, neither with pre-existing health conditions, ate the same meal and one died, he said they were likely to be “adverse” – though the severity of them could vary.

He pointed to a seperate and unrelated case in Victoria last year where two people ate the same meal containing amatoxin, but only one died. It was an apparent reference to a case mentioned earlier in court this week, where a mother who picked mushrooms from the front of her property for a meal she shared with her son died, but her son survived.

Erin Patterson’s family tree. Illustration: Guardian Design

The jury heard in the prosecution’s opening to the case on 30 April that it alleged Patterson did not consume death cap mushrooms at the lunch and pretended she was suffering the same type of illness as the lunch guests “to cover that up”.

Colin Mandy SC, in the defence opening, made clear to the jury that Patterson becoming unwell after the lunch was one of the issues in the trial.

“The prosecution says that Erin Patterson was pretending to be sick and that’s an issue in this trial. The defence case is that she was not feigning illness, she wasn’t pretending to be sick.

“The defence case is that she was sick too, just not as sick. And the defence case is that she was unwell because she’d eaten some of the meal.

“So you’ll need to focus on the evidence as to how that could happen. Is it possible, on the evidence, that she ate some of the meal and not be as sick as the other guests?”

The court heard this week that Patterson told a child protection worker she decided to make beef wellingtons from a RecipeTin Eats cookbook because she wanted to cook something special.

The worker, Katrina Cripps, said Patterson told her that Gail and Don were like the parents she never had, given her own had died, but she felt as if they were being isolated from her by Simon amid a dispute over child support payments.

Cripps told the court Patterson said of this dispute that “as a husband he’d been mean but he’d never been nasty, and she felt that was the time that he’d become nasty”.

Patterson had said “Don and Gail had been like the parents she never had, her parents had died some time ago … but that relationship had changed recently as well” as “she felt that [Simon] was isolating her from his family”, Cripps told the court.

The further illumination of the relationship between Patterson and her in-laws went to something else – something that lingered over the trial after it ended its third week and heard from its 39th witness and something that, as the prosecutor Nanette Rogers SC told the jury, could remain unresolved at the very end of the trial: the question of motive.

Rogers said the prosecution did not need to establish Patterson’s motive in order for the jury to find her guilty. But Mandy said in his opening that in order to resolve the “fundamental issue” of whether Patterson intended to kill her lunch guests, the jury had to consider it.

“Donald and Gail Patterson were the grandparents of Erin’s children, Ian was the pastor of the church that she attended, Heather Wilkinson was part of the extended family and the church community.

Colin Mandy SC for the defence arrives at Latrobe Valley magistrates court. Photograph: James Ross/AAP

“So as you listen to the evidence, you should consider, when it comes to that fundamental issue of Erin’s intention, did she have a motive to kill these four family members?

“What was her relationship with them, especially Don and Gail Patterson? What relationship did her children have with them? That issue, the issue of intention, is the critical issue in this trial.”

There is now one less juror who will decide on that issue, after Justice Christopher Beale discharged Juror 84 from the case.

Beale told the jury he received information that the juror had “been discussing the case with family and friends, contrary to my instructions, and I was of the view that it was at least a reasonable possibility that the information I’d received was credible.

“I want to remind you of my directions that you should only discuss the case with your fellow jurors in the privacy of the jury room; not discuss it with anybody else. It is vital to the administration of justice.

“I hasten to add that I have not made a positive finding that juror number 84 discussed the case with family and friends but neither could I dismiss the possibility that he had. As I said … I was of the view that it was at least a reasonable possibility that he had breached my instructions.”

Beale told the jury at the start of the trial that jurors had previously been imprisoned for breaching the judge’s directions.

On Friday, as the jury rose for the weekend before returning for the fourth week of the trial on Monday, he warned them again: “I don’t want to sound like a broken record”.

The trial continues.