The truth about lie detectors: why Jeremy Kyle's polygraph tests are a cheat - Telegraph.co.uk
The truth about lie detectors: why Jeremy Kyle's polygraph tests are a cheat - Telegraph.co.uk |
- The truth about lie detectors: why Jeremy Kyle's polygraph tests are a cheat - Telegraph.co.uk
- How credible are lie detector tests? - BBC News
- Is a polygraph a reliable lie detector? - Phys.Org
The truth about lie detectors: why Jeremy Kyle's polygraph tests are a cheat - Telegraph.co.uk Posted: 14 May 2019 08:14 AM PDT A guest on the Jeremy Kyle Show has died after taking, and failing, a lie detector test in an attempt to prove that he had not cheated on his fiancée. Steve Dymond apparently died of an overdose a week after failing the test in the studio, and the show has now been cancelled. The validity of lie detector tests has been up for question for a long time. The "polygraph", the most common form of lie detector, works not by detecting actual lies, but by examining physical proxies, such as breathing rate, heart rate, or the skin galvanic response – how much your skin conducts electricity, which correlates with how sweaty you are. This is the kind of lie detector used on the Jeremy Kyle Show, and on... |
How credible are lie detector tests? - BBC News Posted: 04 Oct 2018 12:00 AM PDT In a secure basement room of the US Capitol building, senators are reading a secretive FBI report into allegations of sexual misconduct made against Supreme Court nominee Brett Kavanaugh. The contents of the report are not meant to be revealed, and there has been some criticism that the scope of the investigation has not been wide enough. Throughout the investigation senior Democrats have called for Mr Kavanaugh to take a lie detector test. One of his accusers, Christine Blasey Ford, has already done so. But how accurate are these tests? And how do they work? Let's start with the basics... What is a polygraph test?In short, polygraph tests record a number of different bodily responses which can then be used to determine whether someone is telling the truth. They usually measure things like blood pressure, changes in a person's breathing, and sweating on the palms. "The polygraph, like any other lie detection technique, measures an indirect effect of lying," says Dr Sophie van der Zee, who has expertise in forensic psychology and has researched deception for many years. "There's no human equivalent of Pinocchio's nose," she says. "But lying can increase stress... and with lie detection techniques you can measure the behavioural and physiological changes that occur when you feel stress." So polygraph tests do not measure deception or lying directly, but rather possible signs that a person could be deceiving the interviewer. This information is then used in conjunction with everything else that is known about the person to form a clearer picture of whether or not they are being truthful. How are they carried out?Polygraphs have been used around the world, in countries such as Japan, Russia and China, but the technology remains largely the same. "There's a fairly long pre-test interview that lasts for about an hour," says Prof Don Grubin, who has trained polygraph examiners in the UK. "This focuses the individual on the questions they're going to be asked and tries to remove any outside distractions." This is followed by a practice test, which usually involves a number of straightforward questions. The aim is to relax the individual so they are comfortable and able to understand how the process works. "There are no surprise questions because that in itself will trigger a response," Prof Grubin says. "What you're going to be asked is known." The equipment is then attached, and it usually includes a blood pressure monitor, electrodes which are placed on the fingers or palm, and two tubes which are wrapped around the chest and stomach. "There may be something that's put on the tip of the finger that records blood flow and we also use something called a movement detector which is on the seat and picks up if you're trying to beat the test," Prof Grubin explains. "You'll probably be attached to the equipment for 10-15 minutes but you'll be in the room for about two hours," he says. Interviewers ask a number of control questions during the test and then compare the responses to the key questions. It finishes with a post-test interview, where the person will be able to explain any responses they showed. Can you cheat?Yes, according to the experts. "There's no question that you can beat a polygraph test but you really need the training to do it," says Prof Grubin. "You see websites telling you how to, but the reality is if you just go in and take a polygraph while hoping to beat it then you're not going to." He says that it requires sitting down and practising with a trained examiner. But for those who don't have a qualified questioner to hand - what methods can work? "You might put a tack in your shoe which will cause, for example, a big increase in your sweating response," Prof Grubin says. "Any sort of muscular activity or movement because you need to sit still." "There are various drugs that people try but they tend not to be successful," he adds. But he cautions that most examiners will be able to spot any covert attempt to beat the test. So do they work?The credibility of the polygraph was challenged almost as soon as it was invented in 1921, and there is much debate about its accuracy. Some experts say the fundamental premise is flawed. "It does not measure deception, which is the core problem," says Prof Aldert Vrij, who has written extensively on the subject. "The idea is that liars will show increased arousal when answering the key questions, whereas truth tellers will not. "But there is no sound theory to back this up." Dr van der Zee says that, because taking a lie detector test can be a stressful experience, it can sometimes present innocent people as guilty. "People being interviewed with a polygraph are likely to feel stressed. So whilst the polygraph is quite good at identifying lies, it is not very good at identifying truths," she says. But Prof Grubin says there are a number of different reasons why a test may be inaccurate. These include the questions being poorly formulated and the interviewer misreading the results. "If the examiner is well-trained, if the test is properly carried out, and if there's proper quality controls, the accuracy is estimated between 80%-90%," he says, adding that this is higher than the average person's ability to tell if someone is lying. However, he says that interviewing victims presents a separate problem. "Testing victims is a whole different ball game because of the nature of what they're being asked about, you would expect a lot of arousal anyway," he says. This means a victim, especially one recounting a traumatic experience, may appear as if they are lying because they are in an emotional state. Ultimately, experts say there are many caveats to polygraphs and a number of different factors which can lead to an inaccurate result. |
Is a polygraph a reliable lie detector? - Phys.Org Posted: 01 Oct 2018 12:00 AM PDT Attorneys for Christine Blasey Ford, the woman who's accused Supreme Court justice nominee Brett Kavanaugh of sexual assault, released the results of a polygraph test focused on the decades-old incident. They suggest that Ford's responses to two questions about her allegations were "not indicative of deception." How trustworthy is that assessment and the polygraph technology it relies on? People have long yearned for some way to separate truth from falsehood, whether in high-stakes court cases or family kerfuffles. Over the years, inventors have developed an evolving assembly of tools and instruments aimed at figuring out whether someone is telling a lie. They've tried to incorporate increasingly more science, but with varying degrees of success. Society has often looked to instruments like the polygraph to inject some objectivity into the detection of deception. As a defense lawyer, I've had many a client tell me that he or she did not commit the alleged crime. But I've never asked a client to submit to a polygraph exam: It's high risk, low reward, and the results – while inadmissible in a criminal case – are unpredictable. Just how reliable is a polygraph at identifying who's lying and who's telling the truth? Looking for signs of lies Methods of lie detection have progressed from their torture-centric roots. Early techniques included subjecting someone to a water test: Those who sank were considered innocent, while floating indicated guilt, lies and witchcraft. Neither outcome was good news for the accused. In medieval Europe, an honest man was thought to be able to submerge his arm in boiling water longer than a liar. Eventually people developed more humane methods, focusing on physiological factors that could be used as arbiters of truth. In the early 20th century, William Moulton Marston – self-proclaimed "father of the polygraph" – showed a strong link between systolic blood pressure and lying. Basically, spin a tale and your blood pressure rises. Martson also created the comic book character Wonder Woman, whose golden lasso can extract the truth from those it ensnares. In 1921, physiologist John Larson, from the University of California, Berkeley, was the first to couple measurements of both blood pressure and breathing, looking at rises and drops in respiration. The Berkeley Police Department adopted his device and used it to assess the trustworthiness of witnesses. In 1939, Larson's protégé, Leonarde Keeler updated the system. He made it compact for travel and added a component to gauge galvanic skin response, which measures sweat gland activity that could reflect the intensity of an emotional state. His device, purchased by the FBI, was the precursor to the modern polygraph. Later versions were variations on this original. Lie detectors today "Lie detector" is a broad term. It most often refers to a polygraph, but also applies to a Certified Voice Stress Analysis, an fMRI brain scan, or even software used to analyze the word choice and variation a subject uses when recounting an event. What today's polygraph does is encapsulated in the word itself. "Poly" means many or multiple, and "-graph" means to write. The system records several physiological responses – most often perspiration, heart rate, breathing rate and blood pressure – and graphs them out visually for an examiner to interpret. There are two most common approaches to administering a polygraph. In what's called the Controlled Question Technique, an examiner will ask irrelevant questions, control questions and relevant questions. Then, based on what he sees in the graphical representation of the subject's physiological responses, he will identify whether they change significantly in response to relevant questions. The underlying assumption is that deception will, due to the stress induced by lying, lead to a measurable response in the form of increased perspiration, heart rate and so on. The second approach is known as the Guilty Knowledge Test, which is really a misnomer. It tests any knowledge of events, not just guilty knowledge. The examiner measures a subject's response to specific questions in an attempt to discern whether the subject does in fact have personal knowledge of an event. This could be anything from knowing how many times a victim was stabbed to the color of the getaway car. Presumably, a person who lacks knowledge of an event would not react significantly differently to the accurate answer because he or she wouldn't know what's right and what's not. Meanwhile, so the logic goes, a person who has firsthand knowledge would demonstrate a physiological response. Of course, this method also has inherent limitations regarding, among other things, what types of questions may be presented. Can polygraphs really tell truth from lies? The efficacy of polygraphs is hotly debated in scientific and legal communities. In 2002, a review by the National Research Council found that, in populations "untrained in countermeasures, specific-incident polygraph tests (GKTs) can discriminate lying from truth telling at rates well above chance, though well below perfection." Better than flipping a coin to figure out whether someone is telling the truth, but far from achieving consistent and reliable results. The NRC warned against using polygraphs in employment screenings, but it did note that specific-incident polygraph tests in the field yield more accurate results. It seems targeted, relevant questions – for instance, "Was the robbery committed with a gun?" – meant to unmask a subject who may have a strong motive to lie or conceal information seem to work better. Polygraphs can deliver false positives: asserting that someone is lying who is actually telling the truth. The consequences of "failing" a polygraph can be serious – from not getting a job to being labeled a serial killer. In the 1998 Supreme Court case United States v. Scheffer, the majority stated that "there is simply no consensus that polygraph evidence is reliable" and "unlike other expert witnesses who testify about factual matters outside the jurors' knowledge, such as the analysis of fingerprints, ballistics, or DNA found at a crime scene, a polygraph expert can supply the jury only with another opinion." Notably, litigation over the precursor to the modern polygraph gave rise to the seminal Frye opinion from the D.C. Circuit in 1923, which held that the polygraph evidence was inadmissible in court. In 2005, the 11th Circuit Court of Appeals reiterated that "polygraphy did not enjoy general acceptance from the scientific community." The reality is that multiple factors – including nervousness in a high-stakes situation – can affect the readings detected by a polygraph machine, and give an impression that the subject is lying. For that reason, polygraphs are not generally admissible in any criminal case, even though police interrogators will sometimes trick a suspect into submitting to one. Polygraphs may be admissible in civil cases, depending on the state, and some states allow polygraph tests to be used in criminal cases if everyone agrees to it. Better than nothing? In short, polygraphs may offer some – albeit slight – confidence that a person is telling the truth about a particular incident. Studies have shown that when a well-trained examiner uses a polygraph, he or she can detect lying with relative accuracy. But a polygraph is not perfect: An examiner's interpretation is subjective, and results are idiosyncratic to the person being tested. Under the right circumstances, the polygraph allegedly can be fooled by a trained individual. Even some of my forensic evidence students "beat the test" when I bring a polygraph examiner in for a classroom demonstration. Perhaps the 11th Circuit summed it up best: There is no Pinocchio factor associated with polygraphs. As much as we'd like a sign as obvious as a growing nose, there's no 100 percent reliable physical sign of telling a lie. A polygraph examination demonstrates "that the examinee believes her own story." And perhaps that's enough. A subject's willingness to even submit to an exam often reveals a level of veracity and can fill a void when the other party has not similarly submitted to an exam. Provided by The Conversation This article is republished from The Conversation under a Creative Commons license. Read the original article. Citation: Is a polygraph a reliable lie detector? (2018, October 1) retrieved 19 May 2019 from https://phys.org/news/2018-10-polygraph-reliable-detector.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. |
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