A little more info:
Question:
I have a general question on lie-detector tests. How much credibility does a judge give to this? Is it admissible in court? The police routinely use this as part of their investigative arsenal. I would assume that the reliability of such a test would depend on the person who administers the test. . . . I was curious about your opinion on this.
Response:
I acknowledge receipt of your email inquiry to "Ask the Chief Judge". You have asked about polygraph tests and whether they are admissible in court. You have also asked about their reliability. I will first point out that as a general rule, lie detector test are not admissible in court proceedings, on the basis that evidence of this type may not supersede the role of the court to decide the credibility of a witness: Regina v. Beland & Phillips
While police officers may rely upon such tools to assist them in an investigation, lie detectors operate on the basis that the person is conscious about what is true and what is not, and that a person will react differently when telling a lie than when telling the truth. Testimony in court is often not so simple as the truth or a lie. The ability to observe, record, retain, recall and articulate [that is, put the recollection into words] may intervene to colour or taint a person's testimony. There is sometimes a tendency to "fill in the gaps" in the memory, often without being conscious of doing this. In such a case, the witness would give a sincere, but inaccurate, description of what happened.
Also witnesses may "see" an event differently. For example, a Canucks fan may tend to "see" the calls made against the other team more than the calls made against the Canucks. A fan of the other side would have a different point of view and might have a different recollection of fairness or competence of the officiating.
The lie detector presumes that a person who is lying will have an elevated level of anxiety and exhibit physical symptoms like sweating, increased blood pressure or breathing or heart rates. A sincere but inaccurate or unreliable witness would not believe that what he or she was saying was false so would not react like a person who was intentionally and consciously deceiving. A psychopath, having no conscience, might not be anxious and might appear to be truthful to the lie detector. In each case, the lie detector operator would report that the witness was truthful. As you suggest, the reliability and accuracy of a polygraph may also be dependent on the expertise of the person administering the test.
In court an expert might testify as to the scientific basis of the lie detector and to its validity in detecting liars. Once science has pronounced a witness to be truthful then the judge or jury may tend to accept that witness's testimony without considering whether, in spite of the sincerity of the witness and the expert testimony, there are other factors that may affect the witness's reliability or accuracy.
In this way the lie detector may introduce into the trial an unquantifiable potential for prejudice which would outweigh its value in assisting the judge or jury to come to a just conclusion. In short, polygraphs speak not so much to guilt or innocence but rather to the veracity of the witness.
For more information on the law relating to the credibility of witnesses, you may refer to Chapter 10 of the Legal Compendium on the BC Courts website, at
www.courts.gov.bc.ca/legal_compendium/Chapter10.asp.
Thank you for your inquiry.
Carol Baird Ellan
Chief Judge
Provincial Court of British Columbia