Exceptions of search warrant

In certain cases a search warrant is not required, such as where consent is given by a person in control of the object or property to be searched. 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 properly be 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).
Another exception is when evidence is in plain view - if the officer is legitimately on the premises, his observation is from a legitimate vantage point, and it is immediately apparent that the evidence is contraband (for example, a cannabis cigarette on the front seat of a car while the officer has pulled the suspect over for a seat belt violation), the officer is within his right to seize the object in question.
When police arrest an individual shortly after he exits 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 vehicle which was recently occupied, for weapons or other contraband. (However, a recent Supreme Court decision limits such searches to circumstances where the arrested person has the possibility of accessing the vehicle, or when the vehicle could contain evidence of the crime that the person is being arrested for.) If the subject is arrested in a home, police may search the room in which they were arrested, and perform a 'protective sweep' of the premises where there is reasonable suspicion that other individuals may be hiding. Searches are also allowed in emergency situations where the public is in danger.
With rented property, a landlord may not authorize law enforcement to search a tenant's premises without a search warrant, and a warrant must be obtained under the same guidelines as if it were the tenant's own home. But in some jurisdictions, a hotel room may be searched by consent of the hotel's management without the guest's approval or a warrant.