Amit Katwala
speaker
59 appearances
2 recordings
2 series
first heard Feb 2025
last heard Mar 2025
Amit Katwala’s voice in public audio — every appearance, attributed to the second.
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And does it work? Essentially, the reason the polygraph has been so successful is because of the theater around it, right? It works because people believe it works, so that the mere threat of being attached to a polygraph can compel someone to confess to the crime before the exam even takes place. All this today on Something You Should Know.
That's the principle or the theory, and we'll get into why that maybe isn't necessarily true later on, I'm sure. But yes, the theory is that if you are doing a polygraph exam, you are going to be scared about getting caught.
So when you get asked a question that you know you're going to have to lie on, your pulse will start going up, your blood pressure will go up, you might start breathing differently.
And a skilled polygraph examiner, so the theory goes, should be able to tell the difference between someone who's lying and someone who's telling the truth based on how those things change when they're asked the question.
It depends on the scenario. I think a lot of government jobs in the US still require a polygraph exam. So certain military roles, certain police roles. So some people don't have a choice. That was much more rampant until the late kind of 80s when it was outlawed in commercial enterprises.
But there was a brief period when even companies like McDonald's were doing polygraph tests on their potential employees. For criminal cases, you know, I think sometimes it's presented as a waste for people to clear their name. So I can see why if you are innocent, you might be tempted by that. And maybe if you're guilty, you sort of think, well, you know, I can maybe get away with it.
Exactly. That's a really big kind of flaw in the polygraph. And actually, the polygraph was one of the devices that established the set of standards that we now use to determine whether something is admissible in court or not. It was one of the real test cases where they actually looked at it and they thought, hang on, maybe this isn't really science.
The polygraph machine specifically, which is, I guess, what most people think of now when they think of a lie detector, has its origins in Berkeley, California in the 1920s with the Berkeley Police Department, and a police officer called John Larson. John Larson was a physiologist by training. He wanted to become a criminologist, which is a very new field at that time.
And he took a job in Berkeley because the Berkeley Police Department was led by a kind of visionary police chief called August Vollmer. Vollmer was one of the first...
police chiefs in america to try and bring science or evidence to policing so he gave his officers bikes because he kind of thought that that would enable them to cover more ground he gave them radios he started doing crime mapping and all this kind of pioneering stuff
And as part of that, he also started to hire college graduates as police officers, which was a real revolutionary step at the time in the kind of 1910s, 1920s. So John Marston was one of these college cops, and he and Vollmer came across this paper by a guy called William Marston.
He was a psychologist at Harvard University, and he noticed that when he asked his peers to tell untrue stories, their blood pressure went up. So Larson thought, well, okay, that's an interesting insight, but how can I systematize that? How can I turn that into something objective that can be measured and where the measurements can be recorded so that they can be referred back to you later?
And it's that insight, you know, how can you take this thing that we think we've identified where blood pressure goes up when people lie, how can we turn that into a machine that is objective rather than just based on a single person's observations? So those are the real seeds of the polygraph.
looking at like dormitory thefts at the University of Berkeley. So that was the first case of the polygraph. There was a women's only dorm in Berkeley and a bunch of stuff had gone missing like jewelry and cash and books and things like that. And this was the first case where the Berkeley police department were kind of called in to run polygraph tests on all these young women.
To try and find out who did it. And so John Larson went along with the machine and he ran tests on all these women, including the woman whose stuff had been stolen to begin with. And, you know, eventually he came across a woman who blew up when the machine was connected to her, refused to answer any more questions. And he kind of thought, well, she's the one who did it.
The most recent estimates I have suggest that there are about 3 million lie detector tests a year in the United States. It's used much more heavily in some countries than others. So the US is a very, very heavy user of the polygraph. Japan is another one. So, yes, it was used and it is used. It's still used by government departments, you know, intelligence agencies and things like that.
But it's also used by police departments where they want to get a confession from someone. without necessarily having to take a case to trial. It's a much cheaper way of extracting a confession from someone if you think they're guilty than having to go through this sort of expense and process of actually taking them to trial. So it is still used quite widely.
And you see this in kind of true crime documentaries all the time where the polygraph invariably pops up at some point in the investigation. Its heyday was really in the kind of 20s, 30s, 40s and 50s, I think. So after Larson did these tests on women in college dorms, then they quickly started testing suspected murderers.
And then it kind of snowballed from there with the help of a guy called Leonard Keeler, who was a high school student who really helped to popularize the machine.
Yeah, so the estimates range from as high as 85 to 90 percent to as low as 60 to 65 percent. So it's not much better than tossing a coin. And studies show that actually, as individuals, we can get it. We can tell when someone's lying about 54 percent of the time. So it's only slightly better than just human intuition.
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