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 (amount), 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.
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 his or her 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.
The rules of evidence were developed over several centuries and are based upon the rules from Anglo-Americancommon law brought to the New World by early settlers. Their purpose is to be fair to both parties, disallowing the raising of allegations without a basis in provable fact. They are sometimes criticized as a legal technicality, but are an important part of the system for achieving a just result.
Perhaps the most important of the rules of evidence is that, in general, hearsay testimony is inadmissible (although there are many exceptions to this rule). 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.