Evidence (law) - Relevance and Social Policy

Relevance and Social Policy

Legal scholars of the Anglo-American tradition, but not only that tradition, have long regarded evidence as being of central importance to the law.

In every jurisdiction based on the English common law tradition, evidence must conform to a number of rules and restrictions to be admissible. Evidence must be relevant – that is, it must be directed at proving or disproving a legal element.

However, the relevance of evidence is ordinarily a necessary condition but not a sufficient condition for the admissibility of evidence. For example, relevant evidence may be excluded if it is unfairly prejudicial, confusing, or the relevance or irrelevance of evidence cannot be determined by syllogistic reasoning – if/then logic – alone. There is also general agreement that assessment of relevance or irrelevance involves or requires judgements about probabilities or uncertainties. Beyond that, there is little agreement. Many legal scholars and judges agree that ordinary reasoning, or common sense reasoning, plays an important role. There is less agreement about whether or not judgements of relevance or irrelevance are defensible only if the reasoning that supports such judgements is made fully explicit. However, most trial judges would reject any such requirement and would say that some judgements can and must rest partly on unarticulated and unarticulable hunches and intuitions. However, there is general (though implicit) agreement that the relevance of at least some types of expert evidence – particularly evidence from the hard sciences – requires particularly rigorous, or in any event more arcane reasoning than is usually needed or expected. There is a general agreement that judgments of relevance are largely within the discretion of the trial court – although relevance rulings that lead to the exclusion of evidence are more likely to be reversed on appeal than are relevance rulings that lead to the admission of evidence.

According to Rule 401 of the Federal Rules of Evidence (FRE), evidence is relevant if it has the "tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence."

Federal Rule 403 allows relevant evidence to be excluded "if its probative value is substantially outweighed by the danger of unfair prejudice", if it leads to confusion of the issues, if it is misleading or if it is a waste of time. California Evidence Code section 352 also allows for exclusion to avoid "substantial danger of undue prejudice." For example, evidence that the victim of a car accident was apparently a "liar, cheater, womanizer, and a man of low morals" was unduly prejudicial and irrelevant to whether he had a valid product liability claim against the manufacturer of the tires on his van (which had rolled over resulting in severe brain damage).