As a general rule, searches conducted without a valid search warrant signed by a judge violate the Fourth Amendment, but like most rules of law, there are a number of explicit exceptions. In fact, most searches occur without warrants because police take advantage of these exceptions to the Fourth Amendment.
Police officers are legally allowed to search your home or your property if they obtain a search warrant. To obtain a warrant, police officers must write out an affidavit -- a written statement under oath -- to convince a judge that they have probable cause to believe that criminal activity is occurring at the place to be searched or that evidence of a crime may be found there.
Generally speaking, searches conducted without a warrant are unreasonable because they violate the Fourth Amendment. However, most searches occur without warrants because police take advantage of these legal exceptions to the Fourth Amendment:
- [Consent Searches] If the police ask your permission to search your home, purse, briefcase or other property, and you freely consent, their warrantless search automatically becomes reasonable and therefore legal. Consequently, whatever an officer finds during a consent search can be used to convict the person.
- [Plain View Rule] The Fourth Amendment only applies in places where there is a reasonable expectation of privacy. This is just common sense: Always keep any private items that you don't want others to see out of sight. Legally speaking, police do not need a search warrant in order to confiscate any illegal items that are in plain view. This is further explained in our podcast about the Plain View Rule.
- [Searches Incident To Arrest] Police do not need a warrant to make a search "incident to an arrest". After a legal arrest, police can legally protect themselves by searching the person and the immediate surroundings for weapons that might be used to harm the officer. Consequently, whatever an officer finds during such a search can be used to convict the person. The law has recently changed in this area! For details, listen to the podcast about the U.S. Supreme Court's decision in Arizona v. Gant.
- [Exigent Circumstances] A judge may uphold an officer's warrantless search or seizure if "exigent circumstances" exist. Exigent circumstances were described by one court as "an emergency situation requiring swift action to prevent imminent danger to life or serious damage to property, or to forestall the imminent escape of a suspect or destruction of evidence."