SHOULD I SUBMIT TO A LIE DETECTOR TEST?
My general advice is usually, "No".
The lie detector technology is not recognized by the courts as sufficiently reliable to be admitted into evidence at a trial as to the truth of the answers.
However, it has been my experience that the police frequently believe in the results of that technology, especially where it incriminates the accused person.
I thus have great difficulty in advising anyone to submit to an unreliable technology where the results can be prejudicial.
The results of a lie detector test are not admissible in court. However, the police will usually administer the appropriate cautions and Charter of Rights cautions so that your answers to the questions asked during the test will be recorded and may be admissible in court
R. v. Béland,  2 SCR 398 CanLII
Per Dickson C.J. and Beetz, McIntyre and Le Dain JJ.: The results of a polygraph examination are not admissible as evidence. The polygraph has no place in the judicial process where it is employed as a tool to determine or to test the credibility of witnesses. The admission of such evidence would offend well established rules of evidence, in particular, the rule against oath-helping, which prohibits a party from presenting evidence solely for the purpose of bolstering a witness' credibility, the rule against the admission of past or out-of-court statements by a witness and the character evidence rule. The polygraph evidence is also inadmis- sible as expert evidence. The issue of credibility is an issue well within the experience of judges and juries and one in which no expert evidence is required.
Further, the admission of polygraph evidence will serve no purpose which is not already served. Such admission will disrupt proceedings, will open the trial process to the time-consuming and confusing consideration of collateral issues and will deflect the focus of the proceedings from the fundamental issue of guilt or innocence. It will also lead to numerous complications which will result in no greater degree of certainty in the process than that which already exists. The results recorded by the polygraph instrument, their nature and significance will reach the trier of fact through the mouth of the operator. Human fallibility will thus still be present, but now fortified with the mystique of science.
Per La Forest J.: There are two compelling factors for the exclusion of polygraph evidence in judiciary proceedings: human fallibility in assessing the proper weight to be given to the evidence cloaked under the mystique of science, and the inadvisability of expending time on collateral issues.