Consent Searches. Government officials may conduct a search without a warrant or probable cause based upon an individual's consent, so long as that consent (1) was voluntary and (2) came from someone authorized to give it. Any evidence discovered during a lawful consent search may be seized and admitted at trial. Consent may be express or implied and need not be knowing and intelligent, even though it constitutes a waiver of Fourth Amendment rights.

To determine whether consent was given voluntarily, courts examine the totality of the circumstances. Factors that weigh on the court's determination of voluntariness include: (1) the consenting individual's knowledge of the constitutional right to refuse consent; (2) the consenting individual's age, intelligence, education, and language ability; (3) the degree to which the consenting individual cooperates with the police; (4) the consenting individual's attitude about the likelihood of the discovery of contraband; and (5) the length of detention and the nature of questioning, including police threat of physical punishment or other coercive behavior.

No single factor is dispositive. Moreover, the influence of drugs, intoxication, and mental agitation do not automatically render consent involuntary. Additionally, persons in lawfully-detained vehicles do not have to be advised that they are free to leave before giving voluntary consent. The prosecution bears the burden of proving voluntary consent. Whether consent was voluntary is a question of fact reviewed under a clearly erroneous standard.

Consent is not voluntary if given only in acquiescence to a claim of lawful authority. Therefore, a search may not be justified based on consent given only after the official conducting the search asserts possession of a warrant or the possibility of obtaining a warrant if necessary. In addition, consent cannot justify a search conducted in reliance upon a warrant if a court subsequently determines that the warrant was invalid.

Consent to search is generally invalid if an illegal search or seizure occurred before consent was given. If, however, consent to search is given under conditions sufficiently attenuated from an illegal arrest or search, evidence discovered during the subsequent search will not be suppressed.

In addition to express consent, consent may be implied by the circumstances surrounding the search, the person's prior actions or agreements, or the person's failure to object to the search.

Generally, anyone who has a reasonable expectation of privacy in the place or effects being searched can consent to a warrantless search, and any person with common authority over or other sufficient relationship to the place or effects being searched can give valid consent. However, if two residents are present during the search of their dwelling and one expressly denies consent, the other's consent is not valid. Courts recognize common authority to consent in each person whose mutual use of the property demonstrates “joint access or control for most purposes.” The law presumes that other users of the property assume the risk that areas under common control may be searched. The prosecution bears the burden of establishing that common authority exists.

Moreover, a warrantless search is valid when law enforcement personnel rely on a person's “apparent authority” to consent to the search if the reliance is in good faith and is reasonable based on all facts known by police at the time of the search. Some courts have held that even if a third party is acting as an informant or other agent of the government, that person may still consent to a warrantless search if otherwise empowered to consent.

The scope of a consent search may not exceed the scope of the consent given. The scope of consent is determined by asking how a reasonable person would have understood the conversation between the officer and the suspect or third party when consent was given. Generally, the express object of a search defines the scope of consent, unless the suspect or third party giving consent expressly limits its scope.

Consent to search may be revoked if a person effectively withdraws consent before the search is completed, and police may not continue searching based on prior consent.