Authored by K. Thor Jensen in Gadgets 
Published on 07-31-2009

If you’re reading this, you probably have something to hide. Why else would you need to know how to beat a lie detector? There’s no judgments here, friend – I don’t care what you do with the information I’m about to impart to you. Just try to do something nice for someone else if you get away with it.

First, a little history. The lie detector, or polygraph, was invented in the early 20th century and has been steadily improved upon in the last 100 years. The essential principle of the device is that when a person is lying, there are a number of measureable physical reactions triggered by the unconscious mind. These reactions include an increase in blood pressure, pulse rate, and temperature, as well as the electrical conductivity of the skin. In a typical lie detector test, a number of “control questions” are asked, where the interrogator knows the answers in advance. The responses to these questions establish the subject’s baseline readings, and from there forward each response is measured against the calm “truth” reading to determine whether a lie is being told. However, the polygraph is not a 100% accurate tool, and a prepared, confident subject can manage to fool it. Let’s find out how.

First off, understand the questions you are being asked. Beating a polygraph test isn’t about controlling your reactions when you’re lying, it’s also about controlling them when you’re telling the truth. You will be asked three main types of questions – control questions, known untruth questions, and unknown response questions. Your goal is to make the readout on the control questions match the unknown response questions – so the machine “reads” a lie the same as the truth. There are a number of ways to do this.

One well-documented way to throw off the readings during control questions is by administering small doses of intense pain to your body – the adrenal response that accompanies sudden pain will spike the machine intensely, throwing off the calibration index. Some techniques that people use to pull this off are biting the tongue or inner cheek – not hard enough to draw blood, though, and make sure that this action isn’t detected by your interrogator. Another method is to hide a pushpin in the sole of your shoe, stepping down on it to trigger the flash of pain you need to disrupt the readings. Make sure to do this only when you’re telling the “truth,” though.

The real secret to tricking the polygraph is entirely psychological, however – a lie detector test does more work on your brain than any other part of your body. The people who administer them use a battery of mental tricks to break down your resistance and get you to incriminate yourself of reveal information you would prefer to keep private. You must make sure to not fall for them – while you’re controlling your body’s responses, make sure to keep your mouth in line as well. In reality, much of the power is already in your hands – polygraph responses are not admissible in court, you can’t be released from your place of employment based on their results, and there is a growing scientific and procedural backlash against their use.