Start the scan your fingerprint and say something to see if it is true or a lie. Place your finger on the scanner area and allow scanner begin. Laser Xray will go throught your finger. Use the prank features to fool everyone with this fake lie detector test. Instruction for prank mode: Start by touching and holding friend's finger down on the scan area. First time you see a random result. On result screen tap on the left side of button for “False", and on the right for "True". Pressing the restart button will give a random result. Disclaimer: This application is only a prank trick for fun. it's not a real polygraph lie detector.