Despite claims of 90% validity by polygraph advocates, the National Research Council has found no evidence of effectiveness. ... The American Psychological Association states "Most psychologists agree that there is little evidence that polygraph tests can accurately detect lies."

How accurate is the lie detector test?

There have been several reviews of polygraph accuracy. They suggest that polygraphs are accurate between 80% and 90% of the time. This means polygraphs are far from foolproof, but better than the average person's ability to spot lies, which research suggests they can do around 55% of the time.

Do lie detectors actually detect lies?

Most psychologists agree that there is little evidence that polygraph tests can accurately detect lies.