A sworn statement made in writing.
Example:
Each member of the family had signed an affidavit stating that he or she believed the will to be valid.
In Latin affidavit means "he or she has sworn an oath," and affidavits are always sworn written documents. During the McCarthy era in the 1950s, many people were forced to make affidavits in which they swore that they were not members of the Communist party. Affidavits are usually made without an opposing lawyer being present. When police officers file an affidavit to get a search warrant, they don't inform anyone except the judge of their intent. In this respect, affidavits are different from depositions, which are made with attorneys for both parties present and able to ask questions.