Here in Salt Lake City, the Gwyneth Paltrow ski crash trial was nightly news for the last two weeks. I happened to catch the battle of two experts, which offered some me some interesting insights about how we can decide whether a given expert is right even when we don’t understand the science behind their opinions.
If you haven’t heard of this court case, retired optometrist Terry Sanderson sued the Academy Award-winning actress for injuring him in a ski accident at the Deer Valley Resort in 2016. Conversely, she claimed Sanderson “ran into my F-ing back!”
At first, the case was characterized as “he said, she said.” So how could we tell which story is true?
No Shortage of Self-Identified Experts
It was not hard to find opinions on who was at fault. People on Twitter and YouTube offered:
“Paltrow is a rich, irritating, and arrogant bitch so she must have done it.”
“Sanderson has brain injuries and his family claims his personality changed after the accident, so Paltrow must have run into him.”
“Sanderson is a scammer who is trying to shake down Paltrow.”
“Paltrow is a movie star and business owner, so she must be doing it for publicity even though she is guilty.”
My personal favorite explanation, frequently stated with confidence by social media users, was that since Sanderson was the one who was seriously injured, she must have run into him. This, of course, explains why when skiers slam into a trees they walk away unharmed while the tree is demolished.
Clearly, none of these explanations had any legal, scientific, or even logical basis.
What about the Eyewitness?
Sanderson and Paltrow each took the stand and predictably told completely different stories about what happened. When the litigants tell conflicting stories, we customarily turn to eyewitness testimonies. But there was only one eyewitness, and that witness seemed dubious: He was far from the incident, color blind, and Sanderson’s friend. Moreover, people can be really good liars and studies have shown that eyewitness testimony can be problematic. As a stark example, Carleton University reports:
Eyewitness misidentification has been found to be the leading cause of known wrongful conviction, contributing to approximately 70 per cent of known wrongful convictions that have been overturned by DNA testing
What about Science?
Given the challenge of relying on the sole eyewitness, I started wondering about the science. In the case of a skiing collision, the appropriate science introduced by both litigants was bioengineering, which seeks to apply the laws of physics to show how the impact occurred, how the injuries were caused, and which forces led to the final resting positions of the litigants.
Sanderson’s lawyers put bioengineer Dr. Richard Boehme on the stand. Dr. Boehme had calculated that Sanderson’s injuries could only have occurred if Paltrow hit him. Team Paltrow put bioengineer Dr. Irving Sher on the stand, who alleged that Dr. Boehme’s calculations contained a math error. Thus, Dr. Sher claimed that only Paltrow’s account conformed to the laws of physics.
When Dr. Sher drew some formulas on a whiteboard and went through his calculations, I thought, “Okay that settles it.” But I like math, and unfortunately, Dr. Sher was roundly criticized in the media and on Twitter for writing equations on board. A CourtTV pundit said he “gave the jury a math lesson.” Other people opined, “he didn’t move the needle" and “he confused the jury.”
What were we to do? If separating out the truth required understanding math, how could we expect a jury member to make the right decision? Was the jury just going to choose the more likable expert?
On the final day of testimony, Team Sanderson returned Dr. Boehme to the stand in an effort to salvage their case. Dr. Boehme called in from his vacation and explained that Dr. Sher had assumed Sanderson was free-falling, whereas he most certainly was not. Thus, Dr. Boehme had adjusted his physics formulas to model a person falling from a standing position.
This sounded reasonable—at first.
The only problem? Sanderson’s story was that he was flying through the air. Uh-oh. Paltrow’s attorney quickly pointed that the discrepancy, after which, in a bizarre twist, Sanderson’s own attorney took the microphone and drove it home—fully clarifying to the jury that Sanderson’s story was unsupported by physics. Watch below. You have to see it to believe it!
The free=fall testimony was the most dramatic part of the rebuttal, but other points were also instructional. Not only had Dr. Boehme injected a bit of reality into Sanderson’s story, he had focused solely on the accounts of Sanderson and the eyewitness. He did not take into account a wider set of data, such as the following:
Multiple observers reported that neither party’s ski bindings had broken loose, indicating a slower speed fall, which Sanderson’s story did not support.
Many people arrived quickly at the scene and observed that the heads of the fallen skiers were toward uphill, whereas Sanderson had said they were downhill.
There was newer and more extensive research on how skiing rib fractures occur, which Dr. Sher and taken into account.
Assumptions Matter
So the contention between the experts was not so much about a math error as it was about a difference in assumptions. The learning here is that experts in scientific methods are not necessarily experts in critical thinking. As critical thinkers, we can ask always ask questions about the logic and the assumptions, such as
Which data was included?
What assumptions are you making?
What is the basis of those assumptions?
How did this event lead to the next?
What other evidence would make a difference if you had it?
Thankfully, the jury was also able to sort it out, and Paltrow was declared blameless, as was Dr. Sher. The day after the verdict, juror Samantha Imrie appeared on CNN and stated “Dr. Sher brought it home.”