Usually, consent can be revoked at almost any time during a consent-based search. If consent is revoked, the officer or officers performing the search are required to immediately stop searching. However, the right to revoke consent is not recognized in two specific cases: airport passenger screening and prison visitation.
Withdrawing consent Once consent to search is given, an individual may withdraw or restrict a search. Consent is considered withdrawn if an unequivocal statement is made either through statements, actions, or a combination of both.
Exceptions to revoking consent Most courts have found the right to revoke consent is removed once a passenger has begun
X-ray screening. In
United States v. Herzbrun (1984), the
U.S. Court of Appeals for the Eleventh Circuit found Herzbrun "had no
constitutional right to revoke his consent to a search of his bag once it entered the
X-ray machine and he walked through the
magnetometer." And in
United States v. Pulido-Baquerizo (9th Cir. 1986), the court explained that "[a] rule allowing a passenger to leave without a search after an inconclusive X-ray scan would encourage airline
terrorism by providing a secure exit where detection was threatened." A similar argument is applied to searches of prison visitors, for example, in
United States v. Spriggs (1993). As long as a prison visitor is warned that all visitors will be searched and consents to the search, consent cannot be revoked once the search has begun. Allowing consent to be withdrawn, the court reasoned, would encourage the smuggling of contraband into prisons by providing a secure escape to the smuggler. During the course of a search an officer may develop
reasonable suspicion or probable cause; once this has been developed the individual loses the right to revoke consent. However, in
United States v. Fuentes (1997), the court found the "[m]ere refusal to consent to a stop or search does not give rise to reasonable suspicion or probable cause." ==Cities and states requiring informed consent==