united-kingdom criminal-law england-and-wales civil-law common-law
Which law rules polygraphs inadmissible in UK?
<p>Where does it say that polygraph tests (lie detector tests) are inadmissible under law in England and Wales?</p>
<p>I am mostly interested in their usage being disallowed for criminal (both Magistrates' Court and Crown Court) and civil matters. However, if they were allowed elsewhere, such as for employment tribunals, that would be useful knowledge.</p>

<p><a href="/questions/tagged/canada" class="post-tag" title="show questions tagged &#39;canada&#39;" aria-label="show questions tagged &#39;canada&#39;" rel="tag" aria-labelledby="tag-canada-tooltip-container">canada</a></p>
<p>See <em>R. v. Béland</em>, <a href="https://www.canlii.org/en/ca/scc/doc/1987/1987canlii27/1987canlii27.html" rel="nofollow noreferrer">[1987] 2 S.C.R. 398</a>:</p>
<blockquote>
<p>It is therefore my opinion that evidence of the results of a polygraph examination would clearly offend the rule against the admission of past or out‑of‑court statements by a witness. All of the considerations upon which the rule is based are as applicable to polygraph evidence as to other statements. The repetition of statements by another witness adds nothing to their weight and reliability. The ultimate decision as to the truth or falsity of the evidence of a witness must rest upon the exercise of the judgment of the trier of fact. This is as true of evidence of polygraph tests as of any other evidence. In the last analysis, the trier of fact must reach its conclusion on the basis of the evidence given by a human being in court. The evidence of the polygraph operator if heard by the trier of fact adds nothing to the earlier statement of the witness which is sought to be supported.</p>
<p>...</p>
<p>It was also argued that the polygraph evidence was receivable as expert evidence. The polygraph operator, as an expert, was trained and qualified to give his opinion as to the veracity of the witness, based solely on his interpretation of the significance of the responses made by the witness to the questions put on the examination.</p>
<p>...</p>
<p>Here, the sole issue upon which the polygraph evidence is adduced is the credibility of the accused, an issue well within the experience of judges and juries and one in which no expert evidence is required. It is a basic tenet of our legal system that judges and juries are capable of assessing credibility and reliability of evidence.</p>
</blockquote>
<p><a href="https://law.stackexchange.com/a/94502/46948">Another answer</a> says:</p>
<blockquote>
<p>The real problem with polygrapher's opinions however (like policeman's opinions), is that they simply aren't reliable enough.</p>
</blockquote>
<p>But lack of reliability was not part of the Supreme Court's legal reasoning for rejecting the use of polygraph evidence in court.</p>

<p>What I say during a lie detector test might be considered a valid testimony. But the point of a lie detector test is to identify lies and state that my testimony is not true. &quot;I didn't kill my wife&quot; is valid testimony. That <em>might</em> be considered in court unless it is considered hearsay. The lie detector test saying &quot;he lied, therefore he killed his wife&quot; is not valid testimony. I never said &quot;I killed my wife&quot;, so it's not valid testimony.</p>
<p>You would <em>at least</em> have to have an expert witness who is willing to testify that this machine can beyond a reasonable doubt detect that I am lying, and you won't find that expert witness.</p>
