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Is body language a good crime-solving tool? Science says no.

On Behalf of | Sep 15, 2022 | Criminal law

You’ve likely watched police procedural shows in which a body language expert is able to tell that someone is hiding something. You may have seen books about “how to spot a liar,” or even TED Talks about how to use your own body language to control the messages you are sending to the world.

These are fascinating ideas, and most of us would love to have the ability to detect deception and learn the truth just by “reading” another person’s body language. But does body language interpretation actually work, especially in something so important as a criminal investigation? According to a wide body of scientific and sociological research, the answer is a resounding no.

There is no reliable way to detect lying or deception

Here are statements that many of us have heard so often that we assume they must be true:

  • Failing to make eye contact is a strong indication that someone is lying
  • A person is lying if they touch their nose before answering a question
  • Where a person looks when speaking is an indication of whether they are lying
  • Polygraph tests are a reliable method for detecting deception

None of the above statements are supported by strong evidence, and many have been debunked by studies. When it comes to making or avoiding eye contact, some people who are great liars will actually make more eye contact to “prove” that they are being sincere.

The polygraph test has been used for decades, but it has never been proven to work. It doesn’t measure truthfulness or deception. Instead, it measures how anxious or nervous someone is. A practiced liar may be completely comfortable while an honest person could be anxious simply because they are being interrogated.

According to a recent article in Psychology Today, there is no single piece of body language or test that can reliably detect deception. Humans are complex, and we can’t be read so easily.

Why this is a problem in criminal cases

Despite having almost no supporting evidence and plenty of contradictory evidence, various law enforcement agencies around the country still rely on body language interpretation and polygraph tests to both investigate crimes and secure convictions. These techniques don’t need to be scientifically sound to produce results. As long as juries believe that such tactics are legitimate, prosecutors can present them as evidence to convict individuals of serious crimes.

Until or unless public perception of these techniques changes, wrongful conviction is a very real threat in cases where body language and polygraph tests are presented as proof of guilt.