Can I demand that a witness take a polygraph test?

Can I demand that a witness take a polygraph test?

No, polygraph tests are generally not admissible. What polygraphs tests are, they are often used as an interrogation technique. So I'm a police officer. I say to you, witness or defendant, "Will you take a polygraph test?" Your answer to that, in and of itself, will tell me a lot. If you say, "No I won't," as a police officer I might say, "This person's lying or has something to hide." You can't force somebody to take them. It's a valuable interrogation technique, but in and of itself, not for what the polygraph says, very common myth.