Unit 5—Overview of the Federal Rules of Evidence The law of evidence is a set of rules and principles that govern the admissibility of evidence into various types of judicial and administrative proceedings. Evidence is any matter, verbal, physical or electronic that can be used to support the existence of a factual proposition. One of its main purposes is to protect the jury from being misled. There are two basic categories of evidence, direct and circumstantial. Within these general groups there exist three types of evidence: testimonial, physical, and demonstrative. Any kind of evidence to be considered in a legal context must comply with the admissibility requirements of relevancy and materiality. Direct evidence tends to show the existence of a fact in question without the intervention of proving any other fact: Is the evidence to be believed without inferences or conclusions from it? Direct evidence depends on the credibility of the witness. For example, W testifies that she saw D strangle V with a stocking. W’s testimony is direct evidence on the issue of whether D did in fact strangle V with a stocking, since if that testimony is believed, the issue is resolved. Circumstantial evidence depends on both the credibility of the witness and inferences from the witness. Circumstantial evidence is evidence which, even if believed, does not resolve the matter at issue unless additional reasoning is used to reach the proposition to which the evidence is directed. For example, consider the prosecution of D for strangling V. W, a policeman, testifies that shortly after hearing V’s screams, he saw D running from the scene of the crime, and, after stopping D, found a stocking in D’s pocket. While this testimony is direct evidence on the issues of whether D was at the scene of the crime, was fleeing, and had a stocking in his pocket, it is merely circumstantial evidence as to whether D did the strangling. This is so because only by the application of additional reasoning does the evidence lead to the proposition to which it is addressed. The relevance of proffered evidence differs dramatically depending on whether the evidence is direct or circumstantial. When evidence is direct, so long as it is offered to help establish a material issue, it cannot be irrelevant. Circumstantial evidence, even if offered to prove a material fact, will be found to be irrelevant if the evidence has no probative value, i.e., it does not affect the probability of the proposition to which it was directed. Evidence may be testimonial (witness), physical (tangible objects and parts of the body), or demonstrative. Testimonial evidence is premised upon the witness’ personal knowledge and relies on the person’s five senses. Physical evidence is perceived as indisputable, scientifically sound and most important, neutral. The value of physical evidence cannot be understated. It is the silent, definitive witness. Physical evidence offers certainty and certainty equals proof. In 1953, the criminologist P.L. Kirk wrote that physical evidence cannot be absent because human witnesses are. It cannot perjure itself; only its interpretation can err. Only human failure to find it, study it, and understand it can diminish its value. The means by which physical evidence becomes proof is through forensic science. It often involves submission of some tangible object that was directly involved in the situation or incident (document, passport, weapon, narcotics, drugs, clothing, tax return, blood, hair, etc). Demonstrative evidence serves as an audio-visual aid and is designed to assist the trier of fact in understanding the witness’ testimony. It can include maps, models, x-rays, diagrams, models, computer graphics, statistics, etc.
Authentication requires the party offering contested evidence to provide a basis for the fact finder to believe that the item is what the proponent claims it to be. It