He said the sprouting body of the fungus was most commonly found in April and May but had also been observed in summer and winter months after a period of “decent rainfall”.
Once sprouted, he said, the body of the mushroom would last up to a few weeks, while the mycelium below ground could live for decades or even centuries.
May described the cap of the mushroom as typically “greenish or yellowish but may be whitish or brownish”.
In Victoria, the mycologist said death cap mushrooms were observed most frequently in the metropolitan Melbourne region, particularly in the east.
In the East Gippsland region, May said there had been three reports of death cap mushrooms, one historical record in Morwell and two in April and May 2023 in Outtrim and Loch that were posted to citizen science website iNaturalist.
Questioning also turned to a post made by May on iNaturalist where he identified death cap mushrooms in the locality of Outtrim in the afternoon of May 21, 2023.
May said he was in town to give a presentation to a local community group about fungi when he spotted the growth nearby while walking.
Posting under the name of funkeytom, May said he geolocated the sighting on iNaturalist to within 20m.
“It was in Outtrim and I believe it would have been Neilson St in Outtrim,” he said.
Prosecutors allege the next day, Patterson’s mobile data “suggests” she travelled to Outtrim about 11am before returning to her Leongatha home.
As defence barrister Sophie Stafford cross-examined May, she took him through 10 photographs of possible death cap mushrooms with the expert offering his opinion on whether he was confident he could classify each as such.
He agreed that even for an expert, positively identifying mushrooms “is challenging”.
Quizzed on the possibility of misidentification, May agreed that was why the majority of mushroom poisonings occurred.
Stafford took the witness to a research paper he had co-authored in 2023 that examined the use of phone applications to identify mushrooms and concluded their use for the identification of poisonous species was poor.
He told the jury there was no simple rule that was “totally reliable” to distinguish toxic mushrooms from edible ones.
“After the first fatality of amanita phalloides three decades ago, I was saying ‘just don’t eat wild mushrooms’,” he said.
“Over the years... I would now advocate for this slow mushrooming apprenticeship.”
May told the court calls to the Victorian Poisons Information Centre had risen in recent years and it appears there was an increasing number of people interested in foraging for mushrooms.
“In general, that appears to be the case,” he said.
“The number of calls does seem to be rising but the population of Melbourne is also growing.”
May will continue giving evidence when the trial resumes on Wednesday.
Monash Health director of public health of infections diseases Rhonda Stuart was called to give evidence on Tuesday about her interactions with Patterson on July 31, 2023, two days after the fatal lunch.
She told the court that she was questioned by Patterson on why she was interviewing her, responding: “If the mushrooms she bought were causing a public health issue I’d need to know about it.”
Stuart said Patterson told her that she used two types of mushrooms, fresh from Woolworths and dried from an “Asian grocer”, when preparing the beef Wellington lunch.
“She said they were in a sealed packet but she opened the packet and put them in another container,” Stuart said.
“She said she made a paste, and when I asked her about the dried mushrooms, she said she’d used the entire lot so there was nothing left over.”
Stuart told the court Patterson told her that “she ate about half of the meal”.
Called to give evidence on Tuesday, Monash Health emergency registrar Laura Muldoon told the jury there was no “clinical evidence” Patterson experienced mushroom poisoning on August 1.
According to Muldoon, Patterson had “chapped lips but otherwise she looked perfectly well” and was discharged from hospital later that evening.
Patterson was transferred to Monash Health’s emergency department after self-presenting to Leongatha Hospital on July 31 and complaining of diarrhoea and abdominal cramping.
Quizzed by prosecutor Sarah Lenthall on whether there was any clinical evidence for amanita phalloides poisoning or any other toxin, Muldoon responded “no”.
She told the court that she was tasked with sending remnants of the beef Wellington meal, retrieved from Patterson’s bin, to a mycologist at the Royal Botanical Gardens.
The court was shown a photo depicting pastry with a small amount of brown material separated from the rest of the dish.
Another doctor at Monash Health, Varuna Ruggoo, said Muldoon’s notes said there were “no concerns” about poisoning.
“She wrote in her notes there were no concerns about that kind of poisoning because liver tests were all in normal limits,” she said.
Jurors in the weeks-long trial were told on Thursday last week by trial judge Justice Christopher Beale that they’d be getting a long weekend as a measure expected to save time.
“I’ve just been having a discussion with counsel about the way the case is progressing and the way that we can save some time and we can best achieve that by not sitting on Monday,” he said.
“There are things happening behind the scenes to try and condense the material that will be presented to you and if Monday is devoted to that rather than you sitting here in court listening to some evidence, I expect the case will conclude earlier.”
Patterson is facing trial after pleading not guilty to three counts of murder and one count of attempted murder relating to a fatal lunch she hosted at her home in Leongatha, a small dairy town in Victoria, on July 29, 2023.
Her husband’s parents Don and Gail Patterson, both 70, and Gail’s sister Heather Wilkinson, 66, died after consuming death cap mushrooms inside a beef Wellington that Patterson served.
Wilkinson’s husband Ian Wilkinson, 71, survived after a long stint in hospital.
Patterson’s defence counsel says she did not intentionally or deliberately poison anyone, calling the deaths a tragic accident, and that she too fell sick after eating the lunch.
The trial, now in its third week, continues.
