Evidence that is not directed at a matter in issue in the case is "immaterial." To identify immaterial evidence, ask, "What is my opponent trying to prove?" and then decide whether the thing sought to be proved is a matter in issue.
Regardless of the kind of proceeding, courts or tribunals resolving issues of fact are being asked to settle particular controversies. They are not interested in information about matters other than those that need to be settled. Evidence that is not directed at a matter in issue is inadmissible because it is "immaterial." By contrast, "[evidence] is material if it is directed at a matter in issue in the case."4
Evidence is material if it relates to a primary issue that arises for decision. For example, if the accused is charged only with robbery, proof that the police found child pornography when executing a search warrant at his residence is immaterial. A court will, however, be interested in evidence about whether the accused threatened the victim with bodily harm when taking the money since the substantive law of robbery includes as one of its elements proof that the accused used violence or the threat of violence. If the accused person asks for evidence to be excluded because of an unconstitutional search, the court will become
interested in proof about how the search was conducted. As these examples show, the primary issues that a tribunal has to determine are defined by the pleadings in the case, the substantive laws that pleaded allegations or claims turn on, and those procedural rules that arise during the case that require facts to be determined. Since these are the things the court or tribunal has to resolve to adjudicate the matter before it, evidence about these issues is primarily material and the law of evidence will be receptive to its admission.
A trier of fact cannot resolve primarily material questions of fact without first deciding whether the information it is receiving is accurate. It must therefore assess or judge the quality of the material evidence. Often other evidence can assist the trier of fact in undertaking this assessment. Assume, for example, that the trier of fact is to resolve the material issue of whether the Crown has proved beyond a reasonable doubt that the accused...