Hearsay
A statement made out of court that is offered in court as evidence to prove the truth of the matter asserted.
It is the job of the judge or jury in a court proceeding to determine whether evidence offered as proof is credible. Three evidentiary rules help the judge or jury make this determination: (1) Before being allowed to testify, a witness generally must swear or affirm that his or her testimony will be truthful. (2) The witness must be personally present at the trial or proceeding in order to allow the judge or jury to observe the testimony firsthand. (3) The witness is subject to cross-examination at the option of any party who did not call the witness to testify.
In keeping with the three evidentiary requirements, the Hearsay Rule, as outlined in the Federal Rules of Evidence, prohibits most statements made outside a courtroom from being used as evidence in court. This is because statements made out of court normally are not made under oath, a judge or jury cannot personally observe the demeanor of someone who makes a statement outside the courtroom, and an opposing party cannot cross-examine such a declarant (the person making the statement). Out-of-court statements hinder the ability of the judge or jury to probe testimony for inaccuracies caused by Ambiguity, insincerity, faulty perception, or erroneous memory. Thus, statements made out of court are perceived as untrustworthy.