Introduction To The Law Of Evidence

WHAT EVIDENCE IS?

Most lawyers and students think of evidence as a collection of rules governing what facts may be proved in court, what materials may be placed before the court to prove those facts, and the form in which those materials should be placed before the court. What they have in mind is the law of evidence, but not evidence itself. One of the curiosities of the common law is the emergence of rules of evidence whose purpose is not to enable a party to bring before the court evidence which might help his case, but to prohibit a party from bringing some kinds of evidence if his opponent objects, or even if the court itself refuses to permit it. Because of the demands made by the realities of practice, it is only natural that familiarity with the rules should be emphasized. What is taught and examined in the field of evidence is the law of evidence. Yet there is a whole field of inquiry which relates to evidence itself, rather than the law of evidence. The field is a fascinating mixture of logic, epistemology, sociology, psychology, and the forensic sciences, and is, therefore,

wide enough to encompass a vast library of its own. Its concern is the use of evidence as material

in the reconstruction of past events.

It is a field which has attracted a distinguished, but relatively small number of investigators, at least as far as lawyers are concerned, and some of its main contributors have been philosophers and psychologists. Some of these contributors, for example, Jeremy Bentham, while deeply interested in the science of evidence, actually disapproved of the whole concept of a law of evidence. Bentham perceived rules of evidence to be nothing more than an artificial restriction on the science of evidence, invented by lawyers for less than honorable purposes.John Henry Wigmore, the dean of American evidence writers, required his students to master the science of evidence before turning to the law (a luxury now foreclosed by the tyranny of practice-based syllabus and examinations) and developed a thorough, though cumbersome system for the methodical analysis of evidence to be presented in court. Evidence may be defined in general terms as any material which has the potential to change the state of a fact-finder’s belief with respect to any factual proposition which is to be decided and which is in dispute. 

In more formal terms, Achinstein defines evidence as follows:- 

evidence E is potential evidence on hypothesis H if and only if  ;

(1) E is true; 

(2) E does not make H necessary; 

(3) the probability of H on E is substantial; and

(4) the probability of an explanatory connection between H and E is substantial.

Although, as we shall see, lawyers do not treat evidence in the courtroom with very much deference to the neat compartmentalization of Achinstein’s definition—for example, the question of whether E is true is  decided after rather than before E is legally accepted as evidence, the definition does make clear the logical role of evidence in proving a hypothesis. It is, of course, a logical rather than a legal definition, appropriate to scientific inquiries of any kind. But lawyers have superimposed on it the particular requirements of their own interest in the uses of evidence.