Exceptions to Warrant Requirement

Search incident to lawful arrest note: DNA tests

When officers make an arrest supported by probable cause to hold for a serious offense and they bring the suspect to the police station to be detained in custody, taking and analyzing a cheek swab of the arrestee's DNA is a legitimate police booking procedure that is a reasonable search under the Fourth Amendment.

Stop and Frisk

As noted above , a police officer may stop a person without probable cause for arrest if she has an articulable and reasonable suspicion of criminal activity. In such circumstances, if the officer also reasonably believes that the person may be armed and presently dangerous, she may conduct a protective frisk.

"Automobile" Exception

If the police have probable cause to believe that a vehicle such as an automobile contains contraband or fruits, instrumentalities, or evidence of a crime, they may search the vehicle without a warrant. Rationale: Automobiles and similar vehicles are mobile and so will not likely be available for search by the time an officer returns with a warrant. Moreover, the Supreme Court has declared that people have a lesser expectation of privacy in their vehicles than in their homes. Note: Similarly, if the police have probable cause to believe that the car itself is contraband, it may be seized from a public place without a warrant.

Hot Pursuit

Police officers in hot pursuit of a fleeing felon may make a warrantless search and seizure. The scope of the search may be as broad as may reasonably be necessary to prevent the suspect from resisting or escaping. When the police have probable cause and attempt to make a warrantless arrest in a "public place," they may pursue the suspect into private dwellings.

Exigent Circumstances—Destruction of Evidence

Police officers may enter a home without a warrant to prevent the destruction of evidence, even if the exigency arose because police officers knocked on the door and asked for entry, as long as the officers have reason to believe that evidence is being destroyed and the officers did not create the exigency through an actual or threatened Fourth Amendment violation.

Evanescent Evidence Exception

Police officers may seize without a warrant evidence likely to disappear before a warrant can be obtained. [See Cupp v. Murphy, 412 U.S. 291 (1973)—scrapings of tissues from under a suspect's fingernails, which could be washed away] Whether such a warrantless search is reasonable is judged by the totality of the circumstances.

Emergency Aid Exception

Emergencies that threaten health or safety if not immediately acted upon will justify a warrantless search. This includes situations where the police see someone injured or threatened with injury. Whether an emergency exists is determined objectively, from the officer's point of view. (Some states refer to this as the community caretaker exception.)

Consent

The police may conduct a valid warrantless search if they have a voluntary consent to do so. Knowledge of the right to withhold consent, while a factor to be considered, is not a prerequisite to establishing a voluntary consent.

Search Incident to a Lawful Arrest

The police may conduct a warrantless search incident to an arrest as long as it was made on probable cause.

Plain View

The police may make a warrantless seizure when they: (i) Are legitimately on the premises; (ii) Discover evidence, fruits or instrumentalities of crime, or contraband; (iii) See such evidence in plain view; and (iv) Have probable cause to believe (i.e., it must be immediately apparent) that the item is evidence, contraband, or a fruit or instrumentality of crime.

Exceptions to Warrant Requirement

There are six exceptions to the warrant requirement; i.e., six circumstances where a warrantless search by law enforcement officers is reasonable and therefore is valid under the Fourth Amendment. To be valid, a warrantless search must meet all the requirements of at least one exception.