Fourth Amendment: Search and Seizure — What Police Can and Cannot Do

12 min • Criminal Law

The Fourth Amendment protects against unreasonable searches and seizures and requires warrants to be supported by probable cause. As interpreted by the Supreme Court, the Amendment establishes that warrantless searches are presumptively unreasonable — but there are many important exceptions that police rely on daily.

The key case for understanding when a 'search' occurs is Katz v. United States, 389 U.S. 347 (1967), which established the 'reasonable expectation of privacy' test. Under Katz, a search occurs when government conduct violates a person's actual (subjective) expectation of privacy that society recognizes as reasonable. This test replaced the earlier physical trespass approach from Olmstead v. United States, 277 U.S. 438 (1928).

Major exceptions to the warrant requirement include: consent searches (Schneckloth v. Bustamonte, 412 U.S. 218 (1973)), searches incident to arrest (Chimel v. California, 395 U.S. 752 (1969)), the automobile exception (Carroll v. United States, 267 U.S. 132 (1925)), exigent circumstances, plain view, stop-and-frisk (Terry v. Ohio, 392 U.S. 1 (1968)), and border searches.

The exclusionary rule — established in Weeks v. United States, 232 U.S. 383 (1914), and applied to states in Mapp v. Ohio, 367 U.S. 643 (1961) — generally prohibits the use of evidence obtained through Fourth Amendment violations. However, the good faith exception from United States v. Leon, 468 U.S. 897 (1984), allows evidence obtained through a defective warrant if officers reasonably relied on the warrant.

For self-represented defendants, challenging a search requires filing a motion to suppress under Rule 41. You must have 'standing' — meaning your own Fourth Amendment rights were violated. You can't challenge a search of someone else's property. The burden is initially on the defendant to show a warrantless search occurred; the prosecution must then prove an exception applies.

Key Takeaways

• Fourth Amendment requires warrants based on probable cause, with many exceptions
• Katz: 'reasonable expectation of privacy' test determines if a search occurred
• Key exceptions: consent, search incident to arrest, automobile, exigent circumstances, Terry stop
• Exclusionary rule suppresses illegally obtained evidence, but good faith exception applies
• Challenge illegal searches by filing a motion to suppress — you must have standing

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