Polygraph operator Dee Moody is interviewed by credulous San Mateo County Times staff writer Erin Sherbert. Excerpt:
Q: How do you know if someone is lying or telling the truth, just by a polygraph test?
A: We’re measuring significant changes in your physiological responses. Your responses are involuntary. You can be sitting totally still and your perspiration can change in your finger, and you may not feel it.
Q: Can someone pass the polygraph even if they are lying?
A: The rate of accuracy is about 98 percent. It’s very much dependent on the competency of the examiner, the equipment and whether the examiner is updated on techniques and whether they follow those techniques.
The other 2 percent are usually inconclusive, which means we couldn’t tell. It could be because it’s not readable, or it was all over the place, or we got nothing. That’s when people may have extreme psychological problems or maybe just a really bad cold.
There are also countermeasures. With the Internet today, all you have to do is type in ‘beat the polygraph’ and you can find books for $100 on how to beat the polygraph. But polygraph examiners know about those books, and if they come in and use countermeasures, then we know it.
There are some in that 2 percent who pass when they are guilty or fail when they are not guilty. Those are called false negatives and false positives, but it’s very rare.