I was baffled. I briefly wondered if the hashish was mine and my mind was playing tricks on me. There was the evidence, after all: the lie detector had told me, and the world, that I had lied. Fortunately, my parents still trusted me, though modern science told them not to. They continued to spend money on the lawyer.
Wanting to understand what had gone wrong with the polygraph, I decided to hire a private operator to give me a second test. Somewhere in my files, I still have the letter from him. He said that my test showed evidence of an intent to deceive.
At this point, I began to research polygraphs.
It's always worth remembering that what we call a lie detector test detects stress. It relies on the assumption that there are particular appropriate patterns of stress in lying and truth-telling, and it requires that someone subjectively determine which of those an individual's pattern matches. There's a reason the Supreme Court has decided polygraphs don't meet standards of evidence.
Also entertaining is the polygraph apologist who immediately shows up in the comments of Will's post to call everyone else naive and uninformed without adding any data to the discussion. Whee!