What Is Warrant?
A court order authorizing law enforcement to conduct a search, make an arrest, or seize property. The Fourth Amendment generally requires police to obtain a warrant before searching homes or making arrests, though there are many exceptions.
Quick Answer
A court order authorizing law enforcement to conduct a search, make an arrest, or seize property. The Fourth Amendment generally requires police to obtain a warrant before searching homes or making arrests, though there are many exceptions.
Full Explanation
A warrant is a written order issued by a neutral magistrate or judge authorizing law enforcement to take a specific action — most commonly to search a particular place or arrest a specific person. The warrant requirement flows from the Fourth Amendment, which protects people from unreasonable searches and seizures.
To obtain a warrant, police must present a judge with an affidavit establishing probable cause — a reasonable basis to believe a crime has occurred and that evidence will be found at the location to be searched (for a search warrant) or that the named person committed a crime (for an arrest warrant). The warrant must also describe with particularity the place to be searched and the items to be seized — it cannot be a 'general warrant' allowing a fishing expedition.
However, the warrant requirement has numerous exceptions, and many searches occur without a warrant. Major exceptions include: consent (the person agrees to the search), plain view (evidence is visible in a place police are lawfully located), exigent circumstances (emergency situations where getting a warrant is impractical), search incident to a lawful arrest, automobile exception (lesser expectation of privacy in cars), and stop-and-frisk (brief investigatory stops based on reasonable articulable suspicion).
Evidence obtained through an unlawful search — one that violated the Fourth Amendment — is generally excluded under the exclusionary rule. The 'good faith exception' (United States v. Leon, 1984) allows evidence if police reasonably relied on a facially valid warrant that later proved deficient.
Real-World Example
In Riley v. California (2014), the Supreme Court unanimously held that police cannot search the digital contents of an arrested person's smartphone without a warrant, even though a search incident to arrest normally requires no warrant. The Court found that the vast amount of personal data on smartphones creates privacy interests that outweigh the government's interest in warrantless searches.
In the 2016 San Bernardino iPhone case, the FBI sought a court order requiring Apple to help unlock a terrorist's phone — a case about government search power in the digital age, which ultimately became moot when the FBI found another way in.
Why It Matters for Law Students
The warrant requirement is one of the most litigated areas of constitutional law. The Fourth Amendment and its many exceptions dominate criminal procedure courses and are heavily tested on the bar exam. Understanding what counts as a search, when a warrant is required, and what the exceptions are is fundamental to criminal law practice.