I think there is confusion/conflation with defendants offering to take a polygraph to prove innocence. Sometimes it’s a naive offer sometimes it’s someone who wants to “show proof” they “didn’t do it”.
Sure but it’s usually a PR stunt by the defense “see my client is willing (therefore innocent as no liar would take the test the CIA uses to expose moles)”
“We took a privately administered test by a certified polygraph administrator and my client passed with flying colors!!!”