Death cap mushroom toxins found in lunch leftovers, Erin Patterson murder trial hears

A forensic toxicologist who examined the mushroom paste and meat taken from the leftovers found at Erin Patterson’s home after the fatal beef Wellington lunch said the samples tested positive for death cap mushroom toxins.

Associate Professor Dimitri Gerostamoulos, the head of forensic science and chief toxicologist at the Victorian Institute of Forensic Medicine (VIFM), returned to court on Friday morning to give evidence in the murder trial.

Associate Professor Dimitri Gerostamoulos outside court on Friday. Credit: Justin McManus

Four members of Patterson’s family, including surviving lunch guest Ian Wilkinson, were in court on Friday, watching proceedings from the front row.

Patterson is accused of murdering her parents-in-law, Don and Gail Patterson, and Gail’s sister, Heather Wilkinson, by serving them poisonous mushrooms in a beef Wellington she cooked at her Leongatha home on July 29, 2023.

The Pattersons and Heather Wilkinson died in the days after the meal from the effects of mushroom poisoning. Heather’s husband, Ian, survived after weeks in hospital.

Erin Patterson has pleaded not guilty to three charges of murder and one of attempted murder. Her lawyers have said the deaths were a terrible accident.

Ian Wilkinson, who survived the fatal lunch, arrives at court on Friday.Credit: Justin McManus

On Friday, while under cross-examination by defence barrister Colin Mandy, SC, Gerostamoulos agreed his facility received the lunch leftovers on August 29, 2023. The leftovers were found in a bin at Patterson’s house.

They were then separated onto four trays and sampled.

Mushroom paste and beef samples tested positive for death cap mushroom toxins, he said.

“I can’t comment on the way they’ve been handled, only on the fact we received them in a large ziplock bag,” Gerostamoulos said. He said the VIFM, where the samples were tested, was an accredited facility, which means the integrity of the results could withstand scrutiny.

Gerostamoulos, who has worked in the field for more than three decades and has provided expert evidence for hundreds of cases, noted that while biological samples from Don Patterson and Ian Wilkinson tested positive for death cap mushroom toxins, samples from Gail Patterson and Heather Wilkinson were negative.

This, he said, meant levels were not detectable in the women’s samples – but that didn’t eliminate the possibility the toxin might have been present. He said testing was subject to a threshold level, and anything under the threshold cannot be detected using laboratory equipment.

The expert agreed the following factors could impact how someone recovers from ingesting toxic mushrooms: the amount they consume, the concentration of toxins within the meal, and their general health, age and weight.

Gerostamoulos was also asked what would happen if two adults with no pre-existing health issues ate the same amount of a meal that contained death cap mushrooms.

From left: Don Patterson, Gail Patterson and Heather Wilkinson died from mushroom poisoning. Ian Wilkinson survived after weeks in hospital.

If one died, the prosecution asked what the likely outcome would be for the other person if they survived.

“It would be likely that there would be some adverse outcomes for the person who survived. We have had examples where two people have consumed the same meal,” Gerostamoulos said.

“This happened last year in Victoria, one person passed away and another was ill for some time. It will depend on how much is eaten and the person’s response to the amount of toxins.”

David Lovelock, a plant virologist at Agriculture Victoria, said he received the leftovers on August 2, 2023. He told the jury he was able to detect death cap mushrooms in some of the test tubes provided to him, which contained samples from the dehydrator that Patterson used to dry the mushrooms.

Prosecutor Nanette Rogers, SC, outside court on Friday.Credit: Justin McManus

He said they tested the samples against DNA from Amanita phalloides (the scientific name for death cap mushrooms), ghost mushrooms and yellow staining mushrooms.

“We were able to detect Amanita phalloides in two of the seven test tubes,” he said.

The trial, being heard in the Supreme Court in the Gippsland town of Morwell, continues.

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