What are the basic functions of the polygraph and its legal status in the courts?

In police work, the two major uses of polygraph testing are specific issue testing and preemployment screening. In specific issue testing, the polygraph is used to investigate whether a particular person is responsible for or involved in the commission of a specific offense. Polygraph testing can help to verify information collected during traditional background investigations and to uncover information not otherwise available. The commonly held belief that polygraph examination results are not admitted into evidence in court is untrue. Some courts admit polygraph evidence even over the objection of counsel; in other jurisdictions, polygraph results are admitted by stipulation