Under the Federal Rules of Evidence, only relevant evidence is admissible in court. The standard for relevance is generally low, but the purpose of admitting only relevant evidence is to keep potential evidence within the scope of the trial and limit the amount of time devoted to a case. The Federal Rules contain two regulations devoted to the relevance of evidence: Rule 401 and Rule 402. Rule 402 states that evidence relevant to a case is admissible unless that evidence is precluded under the United States Constitution, a federal statute, the Federal Rules of Evidence, or other rules created by the United States Supreme Court. Irrelevant evidence, under Rule 402, is not admissible.
Rule 401 institutes a test to determine whether evidence is relevant. Under the rule, evidence is relevant if: “(a) it has any tendency to make a fact more or less probable than it would be without the evidence; and (b) the fact is of consequence in determining the action.” The phrase “any tendency” means that the evidence could shift a factfinder’s view of the facts, even if the shift is small in degree. The phrase “more or less probable” allows relevant evidence to come in even if it does not conclusively establish any fact on its own. A fact of consequence means that the fact is related to the cause of action, therefore it must tend to establish a fact that is of consequence to the lawsuit. This allows judges to find admissible evidence while staying within the scope of the legal issues of the case.
As mentioned, irrelevant evidence is inadmissible. However, the relevance bar is a very low hurdle to clear, especially when considering the language of Rule 401(a) by the scope of “any tendency” to make whatever fact in question “more or less probable.” The relevance rule is essentially the starting point to see whether a piece of evidence is admissible, which “opens the door” for potential rebuttable with other evidentiary rules.