Erin Patterson is one of Australia’s worst female killers. But what made her do it?

Erin Patterson tried to portray the image of an innocent mother and loving daughter-in-law, but her hatred for her estranged husband’s family ran deep.

Erin Patterson is one of Australia’s worst female killers. But why she murdered three people and tried to kill another remains unclear. Picture: David Crosling

Erin Patterson tried to portray the image of an innocent mother who accidentally served her lunch guests death cap mushrooms in a beef wellington dish.

But in reality, she had a dark fascination with fungi, an obsession with true crime and a hatred for her estranged husband and his parents.

After a mammoth trial, the jury saw her for what she was: a cold, callous and calculated murderer.

She has now claimed the title as one of Australia’s worst female killers.

But the true motive of her mass murder may never be clear.

From the outset, the prosecution said it would not suggest there was a “particular motive” behind the murders of Don and Gail Patterson and Gail’s sister Heather Wilkinson, as well as the attempted murder of Heather’s husband Ian Wilkinson.

While a motive is helpful to a jury, having one is not essential for a guilty verdict.

In the words of Crown prosecutor Nanette Rogers SC: “People do different things for different reasons. Sometimes the reason is obvious enough to others, at other times, the internal motivations are only known by the person themself.

“You don’t have to know why a person does something in order to know they did it.”

But what is clear is that Patterson’s resentment brewed for some time.

She had a tumultuous relationship with Simon Patterson until the couple finally called it quits in 2015.

The pair remained friends until October 2022 when a dispute arose about child support.

The jury heard she discovered Simon had changed his marital status on his tax return to single and did not tell her for months.

If he had told her earlier, she said, she could have claimed the family tax benefit sooner.

Later that same month, her emotions took over when she thought she had not been invited to Gail’s 70th birthday celebrations.

She sent several abrupt texts to Simon, including one accusing Don of not inviting her.

“Come on, that’s ridiculous. You really reckon dad is lying?” Simon replied.

The pair’s issues continued to fester as they fought over medical bills and school fees for their children.

Patterson needed help so she turned to her in-laws, the loving parents she never had.

But Don and Gail refused, saying they did not want to be their “official mediators”.

Patterson became angry, in fact, she was filled with rage.

Explosive Facebook messages aired during the trial made it evident she resented them.

“Don said they can’t adjudicate if they don’t know both sides and Simon won’t give his side (eye-roll emoji) so he said all he can ask is that Simon and I get together to pray for the children (eye-roll emoji) (eye-roll emoji). This family I swear to f--king god,” she wrote to her online friends.

“I said to him about fifty times yesterday that I didn’t want them to adjudicate (eye-roll emoji) nobody bloody listens to me. At least I know they’re a lost cause.”

In a later message, Patterson wrote: “Don said they tried to talk to him but he refused to talk about it so they’re staying out of it but want us to pray together. I’m sick of this shit I want nothing to do with them.

“I thought his parents would want him to do the right thing but it seems their concern about not wanting to feel uncomfortable and not wanting to get involved in their son’s personal matters are overriding that so f--k em.”

She went on to call Simon “a deadbeat”.

“His mum was horrified I had claimed child support. Why isn’t she horrified her son is such a deadbeat that I had no choice but to claim?”

And it appears Patterson’s true feelings of hatred and disdain persisted into 2023.

Meanwhile, her fascination with fungi and obsession with true crime were simmering in the background.

She had joined Facebook groups dedicated to discussing the high-profile murder trial of former NSW water polo player Keli Lane and devoured true crime content.

Patterson was fascinated by true crime and joined Facebook groups dedicated to discussing the high-profile trial of child murderer Keli Lane.

She had always loved mushrooms for their flavour and nutrition, but at some point, she started to grow fond of them for their poisonous properties.

But one must wonder if the country mum fell in too deep, fantasising about what it would feel like to be the protagonist in her own twisted true crime tale.

Were the parents she never had the easiest targets within her reach?

Who else, other than her children, would willingly eat food around her table?

By April, she had devised a plan to take them out.

As they say, hell hath no fury like a woman scorned.

She researched lethal fungi, foraged death cap mushrooms, cooked them in a hearty beef wellington dish and served them to the unsuspecting Don and Gail.

As for Ian and Heather, they were collateral damage.

The prosecution suggested that she had invited them to the lunch only to ensure her in-laws would attend.

Patterson may have thought she would get away with it – or maybe she never wanted to.

It is possible she craved to sit at the centre of her very own high-profile murder trial.

And as a result, at least one thing has finally crystallised.

Erin Patterson is a heinous triple murderer that deliberately poisoned her estranged husband’s helpless family with the most lethal mushroom in the world.

Originally published as Erin Patterson is one of Australia’s worst female killers. But what made her do it?