4th Amendment Exceptions to search warrant requirement
Police do not need a search warrant, or even probable cause, to perform a limited search of a suspect's outer clothing for weapons, if police have a reasonable suspicion to justify the intrusion—a Terry "stop and frisk".
Under The Border Search Exception custom and immigration officers are not required to have a warrant or probable cause to conduct searches and seizures at international borders and their functional equivalents.
This doctrine is not actually an exception to the Fourth Amendment, but rather to the Amendment's requirement for a warrant or probable cause. Balanced against the sovereign's interests at the border are the Fourth Amendment rights of entrants. Not only is the expectation of privacy less at the border than in the interior, the Fourth Amendment balance between the interests of the Government and the privacy right of the individual is also struck much more favorably to the Government at the border. This balance at international borders means that routine searches are "reasonable" there, and therefore do not violate the Fourth Amendment's proscription against "unreasonable searches and seizures".
Certain cases don't require a search warrant, such as where a person in control of the object or property gives consent. Some commonly cited exigent circumstances are: hot pursuit of a felon (to prevent a felon's escape or ability to harm others); imminent destruction of evidence before a warrant can be properly obtained; emergency searches (such as where someone is heard screaming for help inside a dwelling); or a search incident to arrest (to mitigate the risk of harm to the arresting officers specifically).[8]
Another exception is when evidence is in plain view. In such a case, the officer is legitimately on the premises, his observation is from a legitimate vantage point, and it is immediately obvious that the evidence is contraband. The plain view rule applies—for example—when the officer has pulled the suspect over for a seat belt violation and sees a syringe full of heroin on the passenger seat.
As first established by Carroll v. United States, police are allowed to search a vehicle without a search warrant when they have probable cause to believe that evidence or contraband is located in a vehicle.[9][10] When police arrest an individual shortly after the individual has exited a vehicle, the police may conduct a full search of the suspect's person, any area within that person's immediate reach, and the passenger compartment of the recently occupied vehicle for weapons or any other contraband. However, Arizona v. Gant limits such searches to circumstances where the arrested person could have accessed the vehicle, or when the vehicle could contain evidence of the crime the person is arrested for.[11]
If the subject is arrested in a home, police may search the room where they arrested the subject, and conduct a "protective sweep" of the premises if they reasonably suspect that other individuals may be hiding. The laws also allow searches in emergencies where the public is in danger.
With rented property, a landlord may refuse to allow law enforcement to search a tenant's apartment without a search warrant, and police must obtain a warrant under the same guidelines as if it were a tenant's own home. In some jurisdictions, police may search a hotel room with permission of hotel management but without permission of the guest and without a warrant