First of all, what is a lie detector? It’s also known as a polygraph test.
In movies and TV shows, it is used to decide if a suspect is innocent or guilty. But it’s not quite that simple.
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During a polygraph test, the person being questioned is assessed for heart rate, blood pressure, respiration, and skin conductivity.
Rate and depth of respiration are measured by pneumographs (used to measure volume change during breathing) that are wrapped around their chest. They are also made to wear a blood pressure cuff and two electrodes placed on the fingers or hand.
The person is asked control questions and relevant questions. The measurements from the sensors are recorded (it used to be recorded on paper and is now often done digitally). The polygraph examiner looks at the results and tries to determine whether those measurements indicate if a person is lying.
The problem with polygraph tests
According to the American Psychological Association, there is no evidence that a pattern of physical responses can completely confirm that someone is being deceptive.
It’s used to measure levels of fear and physical responses, not actual lies. These tests can fail because a person who is telling the truth could be anxious and a person who is lying might not be anxious at all.
Dr. Saxe and Israeli psychologist Gershon Ben-Shahar (1999) said, “it may, in fact, be impossible to conduct a proper validity study.”
The APA suggests a reason a polygraph test may appear accurate is that people believe it works and they might confess or feel anxiety when answering the questions. They suggested that if that is true, then the name “a fear detector” might be more accurate.
Can you beat a polygraph test?
The simple answer is, yes. Researchers believe people can beat a lie detector test. This circles back to what was mentioned above, it doesn’t really detect lies. It detects a person’s physical response in the moment.
Meet Douglas Williams
Douglas Williams ran polygraph tests for the police force in Oklahoma City. He said he quickly noticed how the test was used to create fear during an interrogation.
“It’s a psychological billy club that will coerce a person into a confession. It’s not a lie detector, and we’re stupid if we use it as such, but there are occasions when it’s real good to put pressure to bear on a criminal to get a confession,” he said on the Love + Radio podcast.
He said the more heinous the crime is that is under investigation, the more likely an innocent person will fail the test. That’s because the person will be in a state of shock and extremely stressed.
After quitting his job, Williams started moving around the country to campaign against polygraph tests. He shared how he felt they weren’t accurate and talked about the damage they did to innocent people.
He also taught people how he believed the test could be cheated. He said you can pass a polygraph by relaxing on the relevant questions and then thinking of something frightening and tensing certain muscles on the control questions.
“In order for you to pass this test, you’ve got to -- telling the truth has nothing to do with it. You’ve got to produce for the polygraph examiner what he expects to see from a truthful person on this chart. The premise behind the polygraph is that, if you are lying, you will have a reaction on the relevant questions and no reaction on the control questions,” he said on the podcast.
In 1985, Williams testified before Congress for the consideration of Employee Polygraph Protection Act of 1988, which later did become law. It prohibits an employer from requiring or suggesting that an employee or prospective employee take a lie detector test. The law does not cover federal, state, and local government agencies.
Leonard Saxe, a psychologist, also testified before Congress regarding his doubts about the validity of a polygraph test.
“Because of the nature of deception, there is no good way to validate the test for making judgments about criminal behavior. There is no unique physiological reaction to deception,” Saxe said.
Williams created a website and wrote books about how to pass a polygraph test. He held training sessions and charged between $1,000 to $5,000. That was until an undercover operation landed Williams in federal prison. Undercover agents confessed to fake crimes and got Williams to teach them how to pass a polygraph anyway.
In 2015, Williams pleaded guilty to two counts of mail fraud and three counts of witness tampering. He was sentenced to two years in prison.
Williams died on March 19, 2021.
Click here to listen to the episode of This American Life referenced in this article. Click here to listen to the Stuff You Should Know podcast about polygraph tests.