An affidavit is a formal sworn statement of fact, signed by the declarant (who is called the affiant), and witnessed (as to the veracity of the affiant's signature) by a taker of oaths, such as a notary public. The name is medieval Latin for he has declared upon oath.

One use of affidavits is to allow evidence to be gathered from witnesses or participants that may not be available to testify in person before the court.

United States Law

In American jurisprudence, under the rules for hearsay, admission of an unsupported affidavit as evidence is unusual (especially if the affiant is not available for cross-examination) with regard to material facts which may be dispositive of the matter at bar. Affidavits from persons who are dead or otherwise incapacitated, or who cannot be located or made to appear may be accepted by the court, but usually only in the presence of corroborating evidence. An affidavit which reflected a better grasp of the facts close in time to the actual events may be used to refresh a witness' recollection. Materials used to refresh recollection are admissible as evidence. If the affiant is a party in the case, the affiant's opponent may be successful in having the affidavit admitted as evidence, as statements by a party-opponent are not considered hearsay.

Some types of motions will not be accepted by a court unless accompanied by an independent sworn statement or other evidence, in support of the need for the motion. In such a case, the court will accept an affidavit from the filing attorney in support of the motion, as certain assumptions are made, to wit: The affidavit in place of sworn testimony promotes judicial economy. The lawyer is an officer of the court and knows that a false swearing by him, if found out, could be grounds for severe penalty up to and including disbarment. The lawyer if called upon would be able to present independent and more detailed evidence to prove the facts set forth in his affidavit.