What is the legal concept of evidence? When lawyers talk about evidence, what is it that they are referring to? What is it that they have in mind? What are the conditions that the law imposes and must be met for something to be received by the court as evidence?
The legal concept of evidence is neither static nor universal. Medieval understandings of evidence in the age of trial by ordeal would be quite alien to modern sensibilities. What however is certain is that there is no approach to evidence and proof that is shared by all legal systems of the world.
Even within Western legal traditions, there are significant differences between Anglo-American law and Continental European law.
It may seem obvious that there must be a legal concept of evidence that is distinguishable from the ordinary concept of evidence. After all, there are in law many special rules on what can or cannot be introduced as evidence in court, on how evidence is to be presented and the uses to which it may be put, on the strength or sufficiency of evidence needed to establish proof and so forth. But the law remains silent on some crucial matters.
In resolving the factual disputes before the court, the jury or, at a bench trial, the judge has to rely on extra-legal principles. While evidential reasoning in law and in other contexts may share certain characteristics, there nevertheless remain aspects of the approach to evidence and proof that are distinctive to law.
The focus is on how the court weighs the evidence in reaching the verdict. In this connection, three properties of evidence will be discussed: probative value, sufficiency and degree of completeness.
What does Evidence Refer to in Law?
Stephen (1872: 3–4, 6–7) long ago noted that legal usage of the term “evidence” is ambiguous. It sometimes refers to that which is adduced by a party at the trial as a means of establishing factual claims.
“Adducing evidence” is the legal term for presenting or producing evidence in court for the purpose of establishing proof. When lawyers use the term “evidence” in this way, they have in mind what epistemologists would think of as “objects of sensory evidence”. Evidence, in this sense, is divided conventionally into three main categories:
Oral evidence (the testimony given in court by witnesses), documentary evidence (documents produced for inspection by the court), and “real evidence”; the first two are self-explanatory and the third captures things other than documents such as a knife allegedly used in committing a crime.
The term “evidence” can, secondly, refer to a proposition of fact that is established by evidence in the first sense. This is sometimes called an “evidential fact”. That the accused was at or about the scene of the crime at the relevant time is evidence in the second sense of his possible involvement in the crime. But the accused’ presence must be proved by producing evidence in the first sense. For instance, the prosecution may call a witness to appear before the court and get him to testify that he saw the accused in the vicinity of the crime at the relevant time.
The concept of relevance plays a pivotal role in legal fact-finding. Success in proving the presence of the accused (the evidential fact) will depend on the fact-finder’s assessment of the veracity of the witness and the reliability of his testimony. (The fact-finder is the person or body responsible for ascertaining where the truth lies on disputed questions of fact and in whom the power to decide on the verdict vests. The fact-finder is also called “trier of fact” or “judge of fact”. Fact-finding is the task of the jury or, for certain types of cases and in countries without a jury system, the judge.) Sometimes the evidential fact is directly accessible to the fact-finder. If the alleged knife used in committing the crime in question (a form of “real evidence”) is produced in court, the fact-finder can see for himself the shape of the knife; he does not need to learn of it through the testimony of an intermediary.
