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—a judge in bench trials, or the jury in jury cases—in reaching its decision. The law of evidence is also concerned with the quantum (amount), quality, and type of proof needed to prevail in litigation, and the rules vary depending on whether the venue is a criminal court, civil court, or family court, and by jurisdiction. The quantum of evidence refers to the amount required, while the quality of proof concerns its reliability.

Witnesses

Key admissibility rules govern hearsay, authentication, relevance, privilege, witness testimony, opinions, expert testimony, identification, and physical evidence. Standards of evidence range from reasonable suspicion to preponderance of the evidence, clear and convincing evidence, or proof beyond a reasonable doubt. Evidence may take the form of testimony, exhibits, documentary material, or demonstrative evidence.

Ancient and medieval law

Historically, ancient codes like Hammurabi’s required oaths and witnesses, while the Old Testament mandated at least two witnesses for conviction. Roman law allowed judges freedom to evaluate evidence, establishing that proof lies with the affirming party and that suspicion alone cannot convict. Medieval Roman law graded evidence, deeming a single witness or private document as half-proof, which could justify torture for further evidence.

Anglophone (Common) law

In English common law, the jury’s role as fact-finder necessitated exclusionary rules, such as the prohibition on hearsay, to prevent undue influence. The Statute of Frauds and Perjuries in 1677 required written instruments for certain contract claims. Modern legislation in England and Wales now permits hearsay evidence in civil and criminal proceedings, though this can allow false testimony.

Relevance and social policy

Some tribunals, like U.S. military tribunals or Australian health professional tribunals, are not bound by standard evidence rules. Evidence must be relevant to a legal element, but relevance alone is insufficient; evidence may be excluded if unfairly prejudicial or confusing. Assessment of relevance involves judgments about probabilities and common sense reasoning, though scholars disagree on its precise nature.