Polygraphs don’t work, and are inadmissible as evidence.
Not quite accurate - NSA and CIA continue to use them because they are a useful indicator. I would not allow an illegal invader to stay based on passing a polygraph, but I would certainly deport any foreign criminal who failed that test. Polygraphs are not perfect and their admissibility as evidence varies. They are allowed in court in: Alabama, Arizona, Arkansas, California, Delaware, Georgia, Idaho, Indiana, Iowa, Kansas, Nevada, New Jersey, New Mexico, North Dakota, Ohio, Utah, Washington, Wyoming. Additionally, they can be used in California, Arizona, Nevada, Georgia, and Florida, if both parties must agree. Since immigration hearings are not a criminal trial, I'd like to see our Justice Department use polygraphs to streamline the process of deporting invaders.