The polygraph machine, commonly known as the ‘lie detector’, has an aura of scientific certainty in popular entertainment. However, there is no objective device that can determine whether an individual is telling the truth.
The results of a polygraph test are not admissible in criminal court to assist a judge or a jury in assessing the credibility of a witness. Iacobucci, J., speaking for a majority of the Supreme Court of Canada in R. v. Oickle, 2000 SCC 38, at para. 95, notes:
…As many sources have demonstrated, polygraphs are far from infallible... ...this Court recognized in R. v. Beland,  2 S.C.R. 398, that the results of polygraph examinations are sufficiently unreliable that they cannot be admitted in court.
While the results of a polygraph test are inadmissible in criminal court, any statements made by a suspect during the polygraph testing process may be used against him.
There is no legal obligation for an individual to participate in a polygraph test. The police, however, may take advantage of a suspect's misconceptions about the polygraph in an effort to persuade the suspect to give up his right to silence during an interrogation.