What makes evidence inadmissible in court?

Brendan Shea, a DNA expert with the FBI, holds an evidence bag during his testimony in the trial of Washington area sniper suspect John Allen Muhammad. When is a piece of evidence not allowed?
Dave Ellis-Pool/Getty Images

One of the most common forms of relaying gossip or scandalous information is the "h­e said, she said" method. The danger of this practice, of course, is the potential for unreliability: The person telling a story wasn't actually present when the story was unfolding. O­ften, a story can pass around a circle of friends and end up as a mangled form of the truth.

It's a lot like the game "Telephone." In a circle of players, one person whispers a sentence to a neighbor. The neighbor attempts to whisper the same sentence to the next player and so on until the phrase finally reaches its original source. The point of the game is to compare the original sentence with its final version, and chances are the two are quite different. If you've ever played, you might understand the delicate nature of the spoken word and how unreliable hearsay can be.


­Gossip may be fine in the office or at school, but it's a different matter in the courtroom. When lawyers need to convince a judge or jury of the truth or falsity of something, they often provide evidence to back up their claim.

Although almost anything can be considered evidence, whether or not a court gets to contemplate a statement or an object during a trial actually depends on a set of rules. In the United States, The Federal Rules of Evidence, set by Chief Justice Earl Warren in 1965 and made law by Congress in 1975, lay out what makes evidence admissible or inadmissible in court. Although states have their own, slightly different rules regarding evidence, they generally follow the federal guidelines.

What determines whether or not a jury can consider witness testimony? What is hearsay, and does it count in court? Find out what makes evidence inadmissible on the next page.


Admissibility and Inadmissibility


Evidence generally falls into four categories:

  • Real
  • Demonstrative
  • Documentary
  • Testimonial

Real evidence is any actual object that was directly involved in an event in the case. It could be the weapon used to murder a victim, like a gun or a hammer, or the tool used to break into a house, like a crowbar. Demonstrative evidence, on the other hand, is an illustration of evidence -- something like a map of the crime scene. Documentary evidence, also a type of real evidence, describ­es letters, contracts, newspapers or anything that contains human language. Testimonial, or anecdotal evidence, is oral or written evidence from victims, suspects and witnesses involved with the case.


All of the above types of evidence need to follow the rules of admissibility, which are there to make sure that anything introduced to the court as evidence meets three criteria:

  • R­elevance
  • Materiality
  • Competence

Relevant evidence proves or disproves a fact of a crime, but it doesn't necessarily prove anyone's guilt or innocence -- it's simply a broad term that describes any piece of evidence related to the case. A tool stained with a suspect's blood might be relevant, for example, but so is the person who sold that tool to the suspect. However, testimony from a toddler discussing a broken house contract would be deemed irrelevant and therefore inadmissible because a child would be too young to understand the case.

Material evidence, on the other hand, needs to prove an essential fact of the case. For example, if a lawyer attempts to prove that the drapes in the room of a murder scene were blue, chances are a judge will deem such evidence immaterial. The room itself may be relevant to the case, but it's likely the color of the drapes doesn't have anything to do with the murder. Finally, competent evidence is an object or testimony proven to be reliable, like matching fingerprints, the results of a DNA test, or an expert on footwear impressions. An expert giving an opinion that isn't generally accepted in his field, on the other hand, is neither competent nor admissible.

­There's an endless amount of inconsistency and sev­eral exceptions, but one of the most important rules of evidence is the hearsay rule. This rule prohibits secondhand testimony, or evidence of the "he said, she said" variety, during a trial. If an eyewitness to an accident tells his friend the details after the event, the eyewitness's friend's testimony would be hearsay and considered inadmissible.

­A judge can dismiss evidence for several other reasons. A presentation will take an unnecessarily long time; upsetting photographs will unfairly incite a jury, or forensics experts might have gathered evidence illegally. However, the main reason for declaring inadmissibility is to make sure evidence is reliable and fair to both sides of a case. For lots more information on crime and the legal system, see the next page.


Lots More Information

Related­ HowStuffWorks Articles

More Great Links

  • Dicarlo, Vincent. "Summary of the rules of evidence." FindLaw.com, 2001. (June 30, 2008)http://library.findlaw.com/2001/Jan/1/241488.html
  • "Federal Rules of Evidence." Cornell Law School. Effective July 1, 1975. (June 30, 2008)http://www.law.cornell.edu/rules/fre/rules.htm
  • "I­nadmissible evidence." Nolo.com, 2008. (June 30, 2008)­http://www.nolo.com/definition.cfm/Term/2AC3DE52-9273-4C49-BD0FC13728A9CA11/alpha/I/