“Oath or Affirmation”

The Fourth Amendment requires that warrants shall not be issued except on “oath or affirmation” that establishes “probable cause” and that particularly describes “the place to be searched, and the person or thing to be seized.”

Consistent with other usages within the Constitution, the choice of an “oath” or “affirmation” appears designed to allow an alternative for individuals with religious or moral scruples against swearing (e.g., Quakers). Other oaths mentioned in the text of the Constitution include the following: the oath that Article II, Section 1, prescribes for presidents to take on accepting office; the prohibition of religious tests as a qualification for public office in Article VI; and the requirement in Article VI that members of Congress, state legislators, and all state executive and judicial officers shall “be bound by Oath or Affirmation, to support this Constitution.” Oaths were thought to impress individuals with the gravity and solemnity of their duties, and “swearing in witnesses” remains an established part of U.S. judicial procedures, which is designed to promote truth telling.

While written affidavits are the most common form of oaths or affirmations, some states as well as the national government permit individuals to give sworn oral statements via electronic media—like telephones. Such conversations have to be recorded contemporaneously so there is a record, just as there would be if officials had filed written affidavits for warrants.

Court decisions have established that such oral statements can be attested by oath. A Wisconsin Court thus observed in State v. Tye (2001) (quoted in LaFave 2006, 2:521) that “[a]n oath is a matter of substance, not form, and it is an essential component of the Fourth Amendment and legal proceedings.” One test that courts often apply to ascertain whether a statement is made under oath is whether perjury could be charged against someone who knowingly presented falsehoods when offering such testimony, since the threat of such prosecutions is also thought to enhance the likelihood of truth-telling.