Final answer:
A search by the police is considered to occur when they invade a space where an individual has an expectation of privacy, as protected by the Fourth Amendment.
Step-by-step explanation:
A search occurs when the police invade a space in which you have an expectation of privacy. This concept is central to the Fourth Amendment of the U.S. Constitution, which protects individuals from unreasonable searches and seizure.
The requirement for law enforcement to obtain a search warrant is a critical aspect of this protection, designed to ensure that searches are not conducted without probable cause and specific authorization from a judge.
In some cases, such as when there is imminent risk of evidence being destroyed, or when the items are in plain view, a search may be conducted without a warrant. However, the expectation of privacy typically provides the basis for whether a search warrant is necessary.