Polygraph Tests, Faked or False.

Didn't the build team do this already? Granted, they weren't testing how reliable the polygraph is at finding the truth, but IIRC they tried different mythical ways of beating it.

A polygraph just measures various parameters electronically. Not more, not less. Those measurements are as accurate as you can measure stuff electronically.

There are different sensors used to convert "body functions" to electrical signals the polygraph can measure. It can't measure "lies" at all.

A lie causes stress inside the body since it is hard work to come up with a lie that is plausible. When you lie, you double check if the person you have lied to can know that you lie. This stress reaction can be monitored and interpreted.

To determine what is a lie and what isn't is the task of a trained interpreter.

For example when asked how old you are, you need to think about it quickly. Your age isn't fixed so there is no quick memorized answer you can say. Asking for your age is a key question in an investigation since it reveals how a lie would look like.

Many questions answered honestly can cause data identical to what would be caused by a lie. For example if you are insulted by a question or the question makes you worry about something the polygraph will show signs of a possible lie.
A machine "BEEEP - LIAR!" can't exist at all.

A true polygraph interrogation is very complicated since the questions must be simple, harmless, may not be interpreted as implying something and repeated many, many times in different forms. A simple polygraph "lie" test must be done in multiple sittings and involves over a hundred questions to reveal a lie. And then there is no proof that someone had spoken the truth or not, just a chance expressed in a percentage.