Erin Patterson trial: Victoria’s chief toxicologist tells jury death cap mushroom toxins found

Alleged poisoner Erin Patterson used a “RecipeTin Eats cookbook” to prepare the fatal beef wellington dish, her trial has been told.

Giving evidence on Thursday at Ms Patterson’s triple-murder trial, child protection worker Katrina Cripps was questioned about an interview she conducted with Ms Patterson.

Ms Cripps told the jury that Ms Patterson told her she prepared a beef wellington with mashed potato, green beans and a packet gravy for her in-laws.

She was questioned by prosecutor Sarah Lenthall if Ms Patterson told her how she knew to prepare the dish.

“She said that she’d found it in a cookbook, a RecipeTin cookbook, and she wanted to do something new and special,” Ms Cripps responded.

Death cap mushrooms found in Erin Patterson’s dehydrator: court

Taking the witness stand on Friday, Agriculture Victoria research scientist Dr David Lovelock told the court he was enlisted by the Department of Health to conduct DNA analysis on a series of items.

He told the court he was delivered the leftover beef Wellington on August 2, a fruit platter and jug of gravy on August 8 and seven vials of “material” from Ms Patterson’s dehydrator on August 11.

Dr Lovelock said DNA analysis of two samples taken from the lunch did not detect death cap mushrooms.

“The only thing we found was the white button mushroom and bovine material,” he said.

He told the jury the fruit platter was not tested, and no death cap DNA was found in the gravy.

Dr Lovelock said analysis of the seven vials, found two contained material genetically identified as death cap mushroom.

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

“The genetic code we got out of those two samples was more than 99pc similar to a reference sample of amanita phalloides.”

Toxins detected in some lunch guests

Called to give evidence this week, Victoria’s chief toxicologist Dimitri Gerostamoulos said death cap mushrooms primarily contained three toxins – alpha-amanitin, beta-amanitin and gamma-amanitin.

He said testing of samples taken from Ms Patterson and her children and allegedly poisoned lunch guests Don and Gail Patterson and Ian and Heather Wilkinson was conducted by the Victorian Institute of Forensic Medicine. 

The jury was told both alpha-amanitin and beta-amanitin toxins were detected in Mr Patterson’s urine sample taken in hospital the evening of July 30 – about 32 hours after the meal.

Beta-amanitin was detected in a serum sample from Ian Wilkinson taken on July 30 and alpha-amanitin was detected in his urine on August 1 – about 73 hours after the lunch.

Dr Gerostamoulos said no toxins were found in Gail Patterson and Ms Wilkinson’s blood test results, noting no urine sample was provided from the hospital.

The jury was told Ms Patterson had blood and serum samples taken the afternoon of July 31 – about 51 hours following the lunch – with no detection. 

Under cross-examination from defence barrister Colin Mandy SC, Dr Gerostamoulos agreed the toxins were cleared from the blood much faster than in the urine. 

“Yes, that’s our understanding of alpha-amanitin or beta-amanitin, as I said yesterday they have a short half-life,” he said. 

“They persist in urine for a lot longer until urine is removed from the body.”

Toxic dose of death cap mushrooms revealed

Dr Gerostamoulos was quizzed by Mr Mandy on the estimated fatal dose of the amatoxins found in death cap mushrooms.

He said it was estimated to be about 1 milligram per kilogram of body weight, “which is a very small amount”. 

For death cap mushrooms themselves, Dr Gerostamoulos told the jury that for a 70kg adult, a lethal dose was about 50 grams or three tablespoons.

But he agreed there were a lot of variables that could affect whether a dose was lethal, including age, weight, health, care received and the toxic response of an individual.

Dr Gerostamoulos was stood down as a witness after Mr Mady objected to a question by Ms Lenthall.

She questioned that if two adults with no known serious pre-existing health conditions ate the same amount of death cap mushrooms and one person died, what he would expect the health outcome for the second to be.

But an hour later Mr Mandy withdrew his objection and Dr Gerostamoulos responded.

“Yes there would likely be some adverse outcomes to that person,” he said.

“The severity may vary depending on the factors I outlined today.”

Samples tested by Victorian Institute of Forensic Medicine

Dr Gerostamoulos told the court the Victorian Institute of Forensic Medicine was provided with a series of items for testing by police on August 29, 2023 – a month after Ms Patterson hosted a fatal lunch at her Leongatha home.

The items were leftovers from the lunch, a fruit platter, a white jug containing a brown liquid, and vegetable matter or debris located in a dehydrator.

On Thursday, prosecutor Sarah Lenthall told Dr Gerostamoulos the jury a day earlier had heard from mycologist Camille Truong, who examined the leftovers under a microscope and found no traces of death cap mushrooms.

Asked to explain how the Institute’s testing differed, he said “we don’t rely on visual detection of compounds”.

“We rely on sensitive instruments to be able to detect very low quantities that are not visible,” he said.

Death cap toxins found in dehydrator: court

Dr Gerostamoulos said no testing was conducted on the fruit platter, and no amanitins – toxins found in death cap mushrooms – were detected in the brown liquid.

But he said samples of meat, pastry and mushroom paste from the lunch were tested.

In three of four mushroom paste samples no alpha-amanitin or beta-amanitin toxins were found, but in one sample they detected beta-amanitin.

Beta-amanitin toxins were also detected in one meat sample, he said.

In samples supplied of “vegetable matter” located in a dehydrator, Dr Gerostamoulos said both alpha-amanitin and beta-amanitin toxins were detected.

Questioned by Justice Christopher Beale if those toxins were “exclusively” found in death cap mushrooms, Dr Gerostamoulos responded: “Yes.”

Dr Gerostamoulos agreed with a suggestion by Mr Mandy that each of the samples taken of pastry, mushroom paste and meat from the leftovers were not separated to ensure there was only one ingredient. 

“The result needs to be viewed in light of the evidence the sample contains simply more than the mushroom paste?” Mr Mandy questioned. 

“Yes, there may be pastry or beef or what may be,” the toxicologist responded.

Ms Patterson is facing trial after pleading not guilty to the murder of three of her husband’s relatives and the attempted murder of one more.

Simon Patterson’s parents, Don and Gail Patterson, and his aunt Heather Wilkinson died from death cap mushroom poisoning in the week after eating a beef wellington at Ms Patterson’s home on July 29, 2023.

Heather’s husband, Ian Wilkinson, recovered after spending a month and a half in hospital.

Prosecutors allege Ms Patterson deliberately spiked the lunch with “murderous intent”, while her defence argues the case is a “tragic accident”.

The trial continues.