Evidence is perhaps the most important element of any trial in the American judicial system, and entering evidence during a trial is one of the most critical steps in the process. Every state has different rules on what evidence is admissible and on how it must be entered in court, as do the federal courts, but there are some general rules that all U.S. courts observe.
As a matter of definition, evidence is anything that tends to prove or disprove a disputed fact in a legal setting. It can include witness testimony, physical evidence such as blood and DNA, and documents, among others. Some evidence is direct, meaning that if we believe it, it outright resolves the disputed factual issue. Circumstantial evidence, on the other hand, won’t resolve the issue without additional reasoning by jurors or whomever is making the determination. Not all evidence, moreover, is admissible. A complex set of rules determines when entering evidence is allowable.
The broadest, most important rule of entering evidence is the rule of relevance. Relevance basically means any evidence that tends to make a so-called “material fact” more or less like to be true than it would be without the evidence. Material facts are those that are matter in the determination of the fact that is at dispute. Tangential matters, in other words, are considered irrelevant. If a piece of evidence is deemed irrelevant, it is automatically excluded. Before any of the other rules are applied, evidence must survive this requirement.
A second rule in entering evidence is that the party entering a piece of evidence must establish foundation and authenticity. Foundation means, essentially, that the evidence fits within the case the party is making, in other words that there are factual grounds for admitting the evidence. Authenticity simply means the evidence is sufficient to support a finding that it is what the party says it is.
There are special rules, when entering evidence, for witness testimony. In all criminal cases, under the constitution, witnesses must be available for impeachment. In other words, when a witness testifies for one side, the other side must have the opportunity to cross-examine her. This makes it much harder for parties to introduce audio recordings of deposition testimony by witnesses who have died or become unavailable, since opposing parties can’t cross-examine them, though there are exceptions.
Witnesses must also be competent, which means they have the ability to competently observe, recollect and communicate. Problems with memory and communication, as well as mental instability, can lead to findings of incompetency when entering evidence. Child testimony often raises competency questions, since research shows children to be much less reliable witnesses. Witnesses offering expert testimony must meet additional requirements when entering evidence.
One of the biggest rules that governs entering evidence is the hearsay rule. As a general matter, this prevents the admission of evidence that contains a statement made outside of court unless the evidence is provided by the person who made it. In other words, if the person who made the statement can’t or won’t testify to it himself, it’s inadmissible. This rule often typically prevents the admission of damaging statements defendants make to third parties outside of court who then agree to testify.
There are exceptions to the hearsay rule when entering evidence. If a statement is offered for a reason other than to prove the truth of the factual issue in question – such as to demonstrate a party’s state of mind – it may be admissible. Spontaneous confessions may be admissible, as may dying declarations, excited utterances and a number of other types of statements.
Entering evidence in the American judicial system is a complex process, and there are many more rules than these. But the basic requirements are that the evidence must be relevant, it must well-founded, it must be authentic and it must not be hearsay (unless an exception applies). It it’s testimony, it must be competent and subject to impeachment. It it’s another type of evidence, different standards apply. In any event, knowing the rules is key to entering evidence in our court system.