I recently failed 2 polygraphs. The same question caused me to fail both times. "Have you committed a serious crime since the age of 18?" I truthfully have not committed a crime and I answered truthfully when asked. I am not looking for counter measures to pass the test, I am just trying to find out why I failed? Any help would be greatly appreciated.

Hershey05,

The short answer to the question of why you failed the polygraph is that your physiological reactions when asked, "Have you committed a serious crime since the age of 18?" were stronger than your reactions to the "control" question with which used as a basis of comparison. An example of the kind of control question you might have been asked is, "Did you ever knowingly break a rule or regulation?" Polygraphers secretly assume that everyone has broken rule or regulation, but they will maneuver examinees into a denial. They then compare reactions to the control questions with reactions to the relevant questions (like the one about having committed a serious crime). If reactions to the control questions are stronger, the examinee passes. If reactions to the relevant questions are stronger, the examinee fails.

This simplistic methodology has no scientific basis and is inherently biased against the truthful because the more honestly one answers the control questions, and as a result exhibits less physiological responsiveness to them, the more likely one is to fail. For a more detailed explanation of polygraph procedure, see Chapter 3 of The Lie Behind the Lie Detector (1 mb PDF):

https://antipolygraph.org/lie-behind-the-lie-detector.pdf