In Maryland v. Garrison, 480 U.S. 79 (1987), the Supreme Court held that evidence police find while executing a search warrant is not automatically thrown out just because officers searched the wrong place. If the mistake was honest and objectively reasonable, both when the warrant was issued and when it was carried out, the Fourth Amendment is satisfied. Justice Stevens wrote for a 6-3 majority, upholding a Baltimore search that turned up heroin in an apartment the warrant never actually authorized officers to enter.1Justia U.S. Supreme Court Center. Maryland v. Garrison, 480 U.S. 79 (1987)
The Wrong-Apartment Search
Baltimore police were investigating Lawrence McWebb for drug distribution. Working from a reliable informant’s tip, the lead detective checked utility records and looked over the building from the outside. Everything pointed to one apartment on the third floor of 2036 Park Avenue. A magistrate issued a warrant for “the premises known as 2036 Park Avenue third floor apartment” and for McWebb himself.1Justia U.S. Supreme Court Center. Maryland v. Garrison, 480 U.S. 79 (1987)
The third floor actually held two apartments off a shared hallway. One was McWebb’s. The other belonged to Harold Garrison, who had no connection to the drug case. Officers entered through a common door and began searching the floor as a single unit. Inside what turned out to be Garrison’s apartment, they found heroin, cash, and paraphernalia. Only then did they realize the floor was divided in two. They stopped searching Garrison’s unit immediately, but he was arrested and charged under Maryland’s Controlled Substances Act.2FindLaw. Maryland v. Garrison, 480 U.S. 79 (1987)
Garrison moved to suppress the evidence. The case worked its way to the Supreme Court on one question: does an honest mistake about the physical layout of a building destroy an otherwise valid warrant?
The Two-Part Test the Court Adopted
The majority split the Fourth Amendment question in two. First, was the warrant valid when the magistrate signed it? Second, did the officers act reasonably when they carried it out? A search can fail on either prong.
Was the Warrant Valid When Issued?
The Court judged the warrant on what officers knew at the time they applied for it. The Fourth Amendment demands a description specific enough to prevent a general rummage through someone’s property.3Congress.gov. Amdt4.5.1 Overview of Warrant Requirement Here, the officers had corroborated the informant’s tip, examined the building, and pulled utility records. All of it indicated one apartment on the third floor. That made the description as specific as the known facts allowed.
Facts learned later cannot retroactively invalidate a warrant. A warrant supported by probable cause and an honest, reasonably detailed description of the target premises satisfies the Fourth Amendment, even if the description turns out to be factually wrong.1Justia U.S. Supreme Court Center. Maryland v. Garrison, 480 U.S. 79 (1987)
Was the Search Reasonable in Execution?
A valid warrant does not authorize any search officers care to conduct. The manner and scope must stay tied to what the warrant actually covers.4Cornell Law Institute. Particularity Requirement The Court asked whether the officers should have realized sooner that they had wandered into someone else’s home.
The majority concluded they had not. Officers entered through a common door, saw no obvious signs of two residences, and found the drugs before any reason to suspect they were in the wrong unit. Once they realized the floor contained two apartments, they stopped. Because the mistake was both honest and objectively understandable, the seizure did not violate the Fourth Amendment.2FindLaw. Maryland v. Garrison, 480 U.S. 79 (1987)
The Reasonable Mistake Standard
The lasting contribution of the case is the reasonable mistake standard. The test asks whether a reasonably well-trained officer, working with the same information, would have made the same error. If yes, the evidence is generally admissible. If the mistake was one no competent officer would make, the search fails.5Library of Congress. Maryland v. Garrison, 480 U.S. 79 (1987)
The standard operates at both stages. Before the warrant issues, it asks whether the pre-warrant investigation was thorough enough that any factual errors were understandable. During execution, it asks whether officers pushed forward with the mistake longer than a reasonable person would have. An officer who sees clear evidence of a second apartment and keeps searching anyway loses the protection, even if the initial entry was justified.
Lower courts apply this framework to warrants with minor address errors, outdated building descriptions, and similar factual gaps. It gives police room to operate in a world where buildings get subdivided and records lag behind reality. It also sets a real floor. Sloppy investigation and willful ignorance do not qualify as reasonable mistakes.
Where the Dissent Drew the Line
Justice Blackmun, joined by Justices Brennan and Marshall, called the search of Garrison’s apartment a warrantless intrusion into an innocent person’s home, which sits at the core of what the Fourth Amendment protects.5Library of Congress. Maryland v. Garrison, 480 U.S. 79 (1987)
The dissent focused on what the officers failed to do. The detective knew the building had multiple units on other floors. Seven mailboxes and doorbells were visible on the porch. A single question to the informant or to McWebb about the layout could have surfaced the second apartment. In the dissent’s view, those failures fell below reasonable diligence.
Blackmun also disputed the account of the search itself, arguing that the roughly symmetrical layout of the two apartments should have signaled the presence of two residences before officers found the contraband. The disagreement matters because it maps the outer edge of the majority’s rule: how much investigation counts as “enough” is a judgment call that produces different answers in different courtrooms.
How Garrison Fits with Leon and Heien
The case sits inside a broader shift in Fourth Amendment law that began with United States v. Leon, 468 U.S. 897 (1984). Leon held that evidence obtained through an officer’s objectively reasonable reliance on a warrant later found defective should not be excluded, because the exclusionary rule exists to deter misconduct and there is nothing to deter when officers relied in good faith on a judge’s authorization.6Congress.gov. Amdt4.7.2 Adoption of Exclusionary Rule
Garrison extended that logic from legal defects to factual ones. Leon covered warrants a magistrate should not have issued. Garrison covered warrants that described the wrong premises because of an honest factual mistake. Both answer the same way: good-faith reliance on a warrant provides a strong shield, as long as the officers’ conduct was objectively reasonable. The Leon Court also mapped the limits, identifying situations where reliance is not reasonable, including officer dishonesty or recklessness in the affidavit, a magistrate who has abandoned neutrality, and warrants obviously deficient on their face.6Congress.gov. Amdt4.7.2 Adoption of Exclusionary Rule
Nearly three decades later, Heien v. North Carolina, 574 U.S. 54 (2014), extended the logic again, this time to mistakes of law. An officer pulled over a driver for a single working brake light, reasonably believing state law required two. It required only one. The Court held 8-1 that the officer’s reasonable reading of the statute meant the stop did not violate the Fourth Amendment.7Justia U.S. Supreme Court Center. Heien v. North Carolina, 574 U.S. 54 (2014) Together, the three cases mean that both factual and legal errors by police can pass constitutional muster as long as the mistakes are objectively reasonable.
Challenging a Search That Wasn’t an Honest Mistake
If a warrant rested on false or reckless statements rather than a genuine mistake, the primary tool is a motion to suppress under Franks v. Delaware, 438 U.S. 154 (1978). A Franks hearing lets a defendant attack the truthfulness of the affidavit itself.
Getting a hearing requires a substantial preliminary showing that the officer who prepared the affidavit included a false statement knowingly or with reckless disregard for the truth, and that the false statement was necessary to the probable cause finding.8Justia U.S. Supreme Court Center. Franks v. Delaware, 438 U.S. 154 (1978) Vague allegations and a general desire to cross-examine will not do. The defendant must identify the specific false statements and support the challenge with affidavits, sworn witness statements, or a satisfactory explanation for why those are unavailable.
If a hearing is granted and the defendant proves by a preponderance of the evidence that the officer lied or was reckless, the false material is stripped from the affidavit. If what remains cannot support probable cause, the warrant is voided and the evidence is suppressed.8Justia U.S. Supreme Court Center. Franks v. Delaware, 438 U.S. 154 (1978)
The line between Garrison and Franks decides most of these cases. A genuine mistake, like misreading a building’s layout after a reasonable investigation, falls on the Garrison side and the evidence survives. A fabricated or recklessly false statement falls on the Franks side and the evidence goes out. What separates the two, in practice, is how much effort the officer put into getting the facts right before swearing out the affidavit. Challenging a search under Garrison means showing the officers’ mistake was unreasonable, not just that a mistake happened.9Justia. Particularity