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 I guess this comes to the second point, which is it's not really possible to actually assess how accurate the polygraph is when it comes to criminal investigations, because you never actually know what really happened. Say someone gets found guilty with the polygraph, then gets found guilty by a jury and gets sent to prison. That doesn't necessarily mean they were guilty.
So you can never really know. All you can really tell is that in this case, the polygraph agreed with the jury. In this case, the polygraph didn't agree with the jury. But juries are fallible as well. So you can never really tell how accurate the polygraph actually is in the real world rather than lab studies.
Perhaps the easiest way to visualize this is by talking through the equipment that you have attached to you when you have a polygraph test done. So the first thing that you will notice is there's a blood pressure cuff wrapped around your arm. So that's measuring your pulse and also your blood pressure. So how fast your heart is beating and what your blood pressure is doing at the same time.
Then the second thing you'll have is you have two bands wrapped around your chest, one to measure your breathing around the kind of higher up your chest and then one around your diaphragm for lower down. And those are measuring your breathing rate.
So how fast you're taking an air and it's thought that liars might hold their breath while they're formulating a response to a question that they know they're going to have to lie on or things like that. And then the final thing is called galvanic skin response, which is basically sweat. So this is usually attached to the fingertip and this measures how much you're sweating.
So each of those measurements will have a corresponding line on the polygraph chart. And then the examiners will learn to interpret those lines in tandem to look for kind of signs of what they consider to be lying.
Yeah, that's right. Yeah. So and actually, the technology hasn't changed since, you know, the 1920s, really. So in the initial one, yeah, you'd have four different lines on the chart. And then it's the kind of combination of those lines that will appear on the chart, you know, ink on paper or nowadays it's on a computer screen.
Exactly. The machine is supposed to work on the premise that liars will be nervous, but people are nervous for all sorts of reasons, right? There's no way of telling whether someone is sweaty because they're lying or sweaty because they're nervous about being wrongly accused of lying.
Or maybe they're lying, yeah. But you just can't tell. And that's the big problem with the polygraph. Even if 90% of people would show a particular result on the polygraph, that doesn't mean it's true for everyone. And that's the big problem. There's no single telltale sign of lying that works for everyone all of the time. Researchers in the field say there's no Pinocchio's nose.
You know, there's nothing that is going to give you the right answer with enough certainty, enough times to be valid to use in a courtroom setting, for instance.
So it's actually been barred from the courtroom for a really, really long time. So Larson invented the machine in 1921. And there was a famous case called the Fry case, which was set a precedent that the polygraph couldn't be used in the courtroom. And that was actually in, I think, 1923. So it really wasn't long afterwards.
But even the people that invented the polygraph kind of had their misgivings about it quite early on. and thought that it shouldn't have been used as widely as it was being used even back then. So John Larson, who invented it, was really excited about it for the first couple of years. But then he saw how his scientific caution kind of got blown away by hype and press coverage.
And then by the end of his life, he hated the machine. He thought it was like a Frankenstein's monster that he'd unleashed on the world. So I would say that within 10 years, there were serious doubts about the efficacy of the polygraph. But by then, the hype and the you know, the drama around it sort of overtook it all and it really snowballed.
It's very, very subjective. So, yes, you can give two different examiners the same chart to examine and they could come up with completely different answers as to whether the person was lying.
Yes, essentially. That would be my contention. I mean, I think that the machine has obviously helped to put criminals away. There's no getting around that. But the problem is that it's also perpetrated serious miscarriages of justice. Essentially, the reason the polygraph has been so successful is because of the theatre 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 because they're so worried about being found out because they believe the machine works even if it doesn't actually work.
I mean, you don't even need a polygraph machine some of the time. So there's a great story from David Simon's book about policing in Baltimore where he describes the situation. And I think it's recreated in an episode of The Wire, actually, where the police officers didn't have a polygraph available. So they used a Xerox machine.
And they put the subject's hand on a Xerox machine and told the subject that it was a lie detector and then just got the machine to print out a piece of paper with he's lying written on it. And that was enough to kind of trick the suspect into actually, you know, believing that the machine could read their mind.
Exactly. Yes, it does the job. It's all about the theater of it. And actually, they realized this very early on, the inventors of the polygraph, that it was largely about the theater. So they did take steps to amp that up.
Yes. So to train to become a polygraph examiner, well, there's no real regulation stopping you from just buying a polygraph machine on eBay and then advertising your services. But most polygraph examiners that are operating today have certification from something called the American Polygraph Association.
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