What is the Fourth Amendment?
Most search and seizure laws are grounded in the Fourth Amendment, which protects “the right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures.” It also provides that arrest warrants cannot be granted without probable cause. The operative word, here, is “unreasonable,” meaning that reasonable searches are permitted if a judge believes there to be probable cause to search for evidence of a crime, or if particular circumstances make a warrantless search proper. Evidence obtained by government officials (police officers) in violation of the Fourth Amendment is not admissible in a criminal prosecution - this is known as the exclusionary rule, which exist to deter police officers from obtaining evidence in an unlawful manner.
The scope and limitations of search and seizure law will be discussed below.