The Fourth Amendment provides that the government (in most cases, the police) can’t carry out unreasonable searches and seizures. Sometimes searches and seizures require warrants, and sometimes they don’t. (See Search Warrants and Exceptions to the Warrant Requirement.)
If there’s a legal basis for a search—in other words, if the search is reasonable—officers can’t look for any kind of random object they choose. Instead, whether they’re searching pursuant to a warrant or after an arrest, they must limit their searches and seizures to the following kinds of items:
- “Mere evidence.” If the police have probable cause to believe that a piece of evidence is connected to a crime, they can search for and seize it. Examples include fingerprints left at the scene of a burglary and clothing that an eyewitness said a robbery suspect was wearing.
- Instrumentalities of crime. This category applies to items someone used to commit a crime—for example, tools used for a burglary or a computer someone used to hack into a network.
- Fruits of crime. These are essentially criminal proceeds, like stolen items or drug money.
- Contraband. This is property that is itself illegal, like street drugs.
- Weapons. Officers can look for weapons that the suspect used in the crime, might use against them, or might otherwise use to try to escape.
(Warden, Md. Penitentiary v. Hayden, 387 U.S. 294 (1967); United States v. Edwards, 415 U.S. 800 (1974).)