3 Cognitive Biases in Netflix's "Death Cap: The Mushroom Murders" |
On the 29th of July 2023, five people sat down to a home-cooked meal of Beef Wellington in the small town of Leongatha, Australia. Erin Patterson, the cook, was hosting the dinner party for her former parents-in-law, Don and Gail Patterson, and friends Heather and Ian Wilkinson. Within seven days of the meal, Don, Gail, and Heather were dead, and Ian was critically ill in the hospital. The culprit? Amanita phalloides, more commonly known as death cap mushrooms. In September 2025, Erin Patterson was convicted of three counts of murder and one count of attempted murder for serving her guests Beef Wellington containing these toxic mushrooms.
In a Netflix documentary about the case, released in December 2025, Erin’s ex-husband, Eric Patterson, claimed that Erin had previously attempted to poison him a number of times in the past, noting that as one of the reasons he had declined the invitation to the dinner. He didn’t disclose his concerns to his family until after the fatal lunch, leading some to question why he didn’t speak up earlier. This post explores the cognitive biases that may have shaped Eric Patterson’s judgment at the time, which could explain his decision to stay silent.
Korteling et al. (2023) described this bias as the belief that things will always function the way they have done in the past, leading people to underestimate the likelihood of harm and the nature of consequences. In........