Within minutes of Erin Patterson walking into a tiny hospital in rural Victoria, doctor Chris Webster realised she was a cold-blooded killer.

“I knew,” he tells the BBC.

“I thought, ‘Okay, yep, you did it, you heinous individual. You’ve poisoned them all’.”

Dr Webster had spent the morning frantically treating two of the four people a jury this week found Erin had intentionally fed toxic mushrooms – concealed in a hearty beef Wellington lunch served at her home in July 2023.

She was convicted of the murders of her in-laws, Don and Gail Patterson, both 70, as well as Gail’s sister, Heather Wilkinson, 66. Erin was also found guilty of attempting to murder local pastor Ian Wilkinson – Heather’s husband – who recovered after weeks of treatment in hospital.

But initially, when Heather and Ian presented to Leongatha Hospital with intense gastroenteritis-like symptoms, Dr Webster and his team thought they were dealing with a case of mass food poisoning.

Heather had described for him a “lovely” afternoon at Erin’s house, the physician told the trial.

“I did ask Heather at one stage what the beef Wellington tasted like and she said it was delicious,” Dr Webster said.

His suspicion had fallen on the meat, so the doctor took some blood samples as a precaution and sent them off for analysis in a town with better medical facilities, before hooking the Wilkinsons up with fluids.

But soon he would receive a call from the doctor treating Don and Gail at Dandenong Hospital, about a 90-minute drive away, and his stomach dropped.

It wasn’t the meat, it was the mushrooms, she told him. And his patients were on the precipice of an irreversible slide towards death.

He immediately changed tack, beginning treatment to try and salvage their failing livers, and preparing to transfer them to a larger hospital where they could receive specialist care.

It was at this point that someone rang the bell at the front of the hospital.

Through a Perspex security window was a woman telling him she thought she had gastro.

“I’m like, ‘Oh, hang on, what’s your name?’ And she said, ‘Erin Patterson’,” Dr Webster says.

“The penny dropped… it’s the chef.”

He ushered Erin into the hospital and told her he suspected she and her guests were all suffering from life-threatening poisoning from toxic mushrooms. He quizzed her on the source of the fungi included in her home-cooked dish.

“Her answer was a single word: Woolworths,” he says.

“And it all just suddenly coalesced in my brain.”

There were two things that convinced him of her guilt in that moment, Dr Webster explains.

One, it was a far-fetched answer. Admitting she had foraged wild mushrooms, as many locals in the area do, wouldn’t have set off alarm bells. Saying they came from a major grocery chain with stringent food safety standards, on the other hand, was suspicious.

And two, there was no concerned reaction from the mother-of-two – despite being metres from where Ian and Heather, relatives she said she loved, lay on beds desperately sick.

“I don’t know if she even acknowledged their presence,” he says.

Briefly leaving Erin with nurses to undergo some basic health checks, he went to see the Wilkinsons off to Dandenong Hospital. He recalls watching the elderly couple being loaded into an ambulance, Heather calling out to thank him for his care as the vehicle doors were closed.

“And I knew,” he says, trailing off.

“It’s actually quite difficult to talk about without getting emotional.

“She could have quite easily done the complete opposite and screamed… ‘Thanks for nothing’.”

That may have been easier to accept than her sincere gratitude, he says. “You know, I didn’t catch it [the poisoning] earlier.”

But he had no time to process the gravity of their last interaction, rushing back to the urgent care room only to find Erin had discharged herself against medical advice.

After desperately trying to call her on her mobile phone, gobsmacked and concerned, Dr Webster decided to call the police.

“This is Dr Chris Webster from Leongatha Hospital. I have a concern about a patient who presented here earlier, but has left the building and is potentially exposed to a fatal toxin from mushroom poisoning,” he can be heard saying in the call recording, which was played at the trial.

He spells her name for the operator, and gives them her address.

“She just got up and left?” they ask. “She was only here for five minutes,” Dr Webster replies.

At her trial, Erin said she had been caught off guard by the information and had gone home to feed her animals and pack a bag, pausing to have a “lie down” before returning to the hospital.

“After being told by medical staff you had potentially ingested a life-threatening poison, isn’t it the last thing you’d do?” the prosecutor asked her in court.

“It might be the last thing you’d do, but it was something I did,” Erin defiantly replied from the witness stand.

But before police reached her house, Erin had returned to hospital voluntarily. Dr Webster then tried to convince her to bring in her children – who she claimed had eaten leftovers.

“She was concerned that they were going to be frightened,” he said in court.

“I said they can be scared and alive, or dead.”

Erin told the jury she wasn’t reluctant, rather overwhelmed by the doctor who she believed was “yelling” at her. “I’ve since learnt this was his inside voice,” she added.

Dr Webster clocked off shortly after, but the trial heard medical tests performed on Erin and her children would return no sign of death cap poisoning, and after a precautionary 24 hours in hospital, they were sent home.

Two years later, when news of the jury’s verdict flashed on his phone on Monday, Dr Webster began shaking.

He was one of the prosecution’s key witnesses, and had struggled with the “weight of expectation”.

“If the picture is going to make sense to the jury, if a small puzzle piece is out of place, it could upset the whole outcome of the trial… I really didn’t want to crack under the scrutiny.”

It’s a “relief” to have played his part in holding Erin Patterson – who he calls “the definition of evil” – accountable.

“It does feel like [there’s] that reward of justice.”

For him though, the biggest sense of closure came from seeing Ian Wilkinson – the only surviving patient – for the first time since sending him and his ailing wife off in an ambulance.

“That memory of Heather being sort of taken away in that fashion, that’s now bookended by seeing Ian standing on his feet again.”

“That brought some comfort.”