We all tell lies but have you wondered how a lie detector works lie detector was invented by John Landon in 1921. He was a medical student of University of California it is based on your blood pressure,pulse rate and skin resistance that is how much your skin is  sweating. Let's talk about this test. This test generally comprises of yes or no questions and in this test two electron rodes are connected to your fingers to regulate electric current through your body. As much as you tell lie now you will sweat which in turn create an equivalent amount of current this process is known as galvanic skin response. This also measures the amount of expansion and contraction of your chest as well as breath rate. This all lead to conclusion. Whether you are lying or not.
This is how a lie detector works