-Some people have higher stress and some have low, and averages change from day to day along with mood. What all people have in common is that their stress levels are constantly changing within their current range - changes which indicate the "perceived jeopardy" or "danger" of statements being made. A lie is often dangerous, humiliating, or injurious to get caught at, so lies tend to stand out on stress measurements

-In moments of stress, like when you tell a lie that you dare not get caught at, the body prepares for fight or flight by increasing the readiness of its muscles to spring into action. Their vibration increases from the relaxed 8 to 9 Hz, to the stressful 11 to 12 Hz range. -It's not the 'lie' itself, but the fear, unease or other emotional stress about a 'deceitful lie', that causes the visual or audio alerts in voice stress and voice emotional analysis.

-A person with no compunction could tell extensive casual lies to these programs with no response - as is evident in testing with 'mock' scenarios. But when the same person talks of significant matters, these programs detects the stress.

VSA consumer applications include public freeware like TruthVSA3 (Windows), Prevaricator (Windows), LiarLiar (Linux) and ShakyVoice (PPC). Or, you can also purchase software like Ex-Sense (windows), Fortress (Windows - 'abandonware'), LieSpy (Nokia only), KishKish (Skype), or X13-VSA (Windows) – all available on the Internet.

You do it all yourself or use a service, but the most critical issue for good feedback is a good audio recording of your subjects' responses. There are some simple, but very important guidelines to follow:

-Relaxed, Non-threatening Atmosphere: (less controlled environments)

-No 'Mock' Testing: Never attempt to apply testing in 'mock' (made-up) scenarios (i.e. never ask how the subject feels in an 'imagined' situation)

-Take a "positive" approach: Apply the overall approach with the PRIMARY intention of confirming that your subject is not deceitful when making a statement or responding to a question; Candid recording is best; Next best is cleverly staging in questions and answers