A polygraph is just an intimidation tool. I have family who worked for 3-letter agencies who “failed” polygraphs, only to have them retaken a day later and “pass”. The polygraph examiners are pretty darn good at intimidating subjects, which understandably affects their vitals, causing false positives left and right. Heck, I have a 30-40 mmHg higher blood pressure reading in any doctor’s office than I do at home due to white coat syndrome. I can’t imagine how being interrogated would for something I didn’t do would affect me.