Evidence (law)
The law of evidence, also known as the rules of evidence, encompasses the rules and legal principles that govern the proof of facts in a legal proceeding. These rules determine what evidence must or must not be considered by the trier of fact in reaching its decision. The trier of fact is a judge in bench trials, or the jury in any cases involving a jury. The law of evidence is also concerned with the quantum, quality, and type of proof needed to prevail in litigation. The rules vary depending upon whether the venue is a criminal court, civil court, or family court, and they vary by jurisdiction.
The quantum of evidence is the amount of evidence needed; the quality of proof is how reliable such evidence should be considered. Important rules that govern admissibility concern hearsay, authentication, relevance, privilege, witnesses, opinions, expert testimony, identification and rules of physical evidence. There are various standards of evidence, standards showing how strong the evidence must be to meet the legal burden of proof in a given situation, ranging from reasonable suspicion to preponderance of the evidence, clear and convincing evidence, or beyond a reasonable doubt.
There are several types of evidence, which vary from one another in form or source.
Evidence governs the use of testimony, exhibits, documentary material, or demonstrative evidence, which are admissible in a judicial or administrative proceeding.
When a dispute, whether relating to a civil or criminal matter, reaches the court there will always be a number of issues which one party will have to prove in order to persuade the court to find in their favour. The law must ensure certain guidelines are set out in order to ensure that evidence presented to the court can be regarded as trustworthy.
History
Ancient and medieval law
had some evidence requiring an oath and witness. See specifically laws 10, 11, and 12.The Old Testament demanded at least two witnesses for conviction of a crime.
Ancient Roman law allowed freedom to judges to evaluate evidence, but insisted that "proof is incumbent on the party who affirms a fact, not on him who denies it" and "no-one should be convicted on suspicion". Medieval Roman law developed an elaborate grading of degrees of evidence. Building on the Biblical two-witness rule, it concluded that a single witness, or private documents, could constitute half-proof, which though insufficient for conviction might justify torture to extract further evidence. Because evidence in the continental system was evaluated by judges rather than juries, that system did not develop exclusionary rules of evidence in the way English law did.
Anglophone (Common) law
A distinct feature of English common law historically was the role of the jury as a finder of fact, as opposed to the role of the judge as finder of law. The creation of modern jury trials in the 16th and 17th centuries necessitated rules of evidence to regulate what testimony and other evidence could be put before the jury. While much of the early common law evidence rules came from judicial decisions, the English Parliament also played a role. In 1677, Parliament and the Crown enacted the Statute of Frauds and Perjuries, prohibiting plaintiffs from alleging certain contractual breaches to the jury unless accompanied by a signed, written instrument. Another early evidence rule was the prohibition on hearsay, the admission of an out-of-court statement to prove the truth of what is asserted. In the early 19th Century, Chief Justice Lord Mansfield of the Court of Common Pleas stated:"In Scotland and most of the continental states, the judges determine upon the facts in dispute as well as upon the law; and they think there is no danger in their listening to evidence of hearsay, because, when they come to consider their judgment on the merits of the case, they can trust themselves entirely to disregard the hearsay evidence, or to give it any little weight which it may seem to deserve. But in England, where the jury are the sole judges of the fact, hearsay evidence is properly excluded, because no man can tell what effect it might have upon their minds."Hearsay rules have subsequently been updated numerous times. Most recently in England and Wales, the Civil Evidence Act 1995, section 1, specifically allows for admission of 'hearsay' evidence; legislation also allows for 'hearsay' evidence to be used in criminal proceedings, which makes it possible for the accuser to induce friends or family to give false evidence in support of their accusations because, normally, it would be rejected by the presiding authority or judge. There are several examples where presiding authorities are not bound by the rules of evidence. These include the military tribunals in the United States and tribunals used in Australia to try health professionals.
Relevance and social policy
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, i.e. 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 logical analysis. 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 agreement that the relevance of at least some types of expert evidenceparticularly evidence from the hard sciencesrequires 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, 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.
Presence or absence of a jury
The United States has a very complicated system of evidentiary rules; for example, John Wigmore's celebrated treatise on it filled ten volumes. James Bradley Thayer reported in 1898 that even English lawyers were surprised by the complexity of American evidence law, such as its reliance on exceptions to preserve evidentiary objections for appeal.Some legal experts, notably Stanford legal historian Lawrence Friedman, have argued that the complexity of American evidence law arises from two factors: the right of American defendants to have findings of fact made by a jury in practically all criminal cases as well as many civil cases; and the widespread consensus that tight limitations on the admissibility of evidence are necessary to prevent a jury of untrained laypersons from being swayed by irrelevant distractions. In Professor Friedman's words: "A trained judge would not need all these rules; and indeed, the law of evidence in systems that lack a jury is short, sweet, and clear." However, Friedman's views are characteristic of an earlier generation of legal scholars. The majority of people now reject the formerly-popular proposition that the institution of trial by jury is the main reason for the existence of rules of evidence even in countries such as the United States and Australia; they argue that are at work.
Exclusion of evidence
Unfairness
Under English law, evidence that would otherwise be admissible at trial may be excluded at the discretion of the trial judge if it would be unfair to the defendant to admit it.Evidence of a confession may be excluded because it was obtained by oppression or because the confession was made in consequence of anything said or done to the defendant that would be likely to make the confession unreliable. In these circumstances, it would be open to the trial judge to exclude the evidence of the confession under Section 78 of the Police and Criminal Evidence Act 1984, or under Section 73 PACE, or under common law, although in practice the confession would be excluded under section 76 PACE.
Other admissible evidence may be excluded, at the discretion of the trial judge under 78 PACE, or at common law, if the judge can be persuaded that having regard to all the circumstances including how the evidence was obtained "admission of the evidence would have such an adverse effect on the fairness of the proceedings that the court ought not to admit it."
In the United States and other countries, evidence may be excluded from a trial if it is the result of illegal activity by law enforcement, such as a search conducted without a warrant. Such illegal evidence is known as the fruit of the poisonous tree and is normally not permitted at trial.