Knowles v. Iowa (1998)

Supreme Court of the United States

Patrick Knowles v. Iowa

Decided Dec. 8, 1998 – 525 U.S. 113

Chief Justice REHNQUIST delivered the opinion of the Court.

An Iowa police officer stopped petitioner Knowles for speeding, but issued him a citation rather than arresting him. The question presented is whether such a procedure authorizes the officer, consistently with the Fourth Amendment, to conduct a full search of the car. We answer this question “no.”

Knowles was stopped in Newton, Iowa, after having been clocked driving 43 miles per hour on a road where the speed limit was 25 miles per hour. The police officer issued a citation to Knowles, although under Iowa law he might have arrested him. The officer then conducted a full search of the car, and under the driver’s seat he found a bag of marijuana and a “pot pipe.” Knowles was then arrested and charged with violation of state laws dealing with controlled substances.

Before trial, Knowles moved to suppress the evidence so obtained. He argued that the search could not be sustained under the “search incident to arrest” exception because he had not been placed under arrest. At the hearing on the motion to suppress, the police officer conceded that he had neither Knowles’ consent nor probable cause to conduct the search. He relied on Iowa law dealing with such searches.

[Under Iowa law at the time, when an officer was authorized to arrest someone for a traffic offense but instead issued a citation, “the issuance of a citation in lieu of an arrest” did “not affect the officer’s authority to conduct an otherwise lawful search.”]


[W]e [have] noted the two historical rationales for the “search incident to arrest” exception: (1) the need to disarm the suspect in order to take him into custody, and (2) the need to preserve evidence for later use at trial. But neither of these underlying rationales for the search incident to arrest exception is sufficient to justify the search in the present case.


[T]he authority to conduct a full field search as incident to an arrest [is] a “bright-line rule,” which [is] based on the concern for officer safety and destruction or loss of evidence, but which [does] not depend in every case upon the existence of either concern. Here we are asked to extend that “bright-line rule” to a situation where the concern for officer safety is not present to the same extent and the concern for destruction or loss of evidence is not present at all. We decline to do so. The judgment of the Supreme Court of Iowa is reversed, and the cause is remanded for further proceedings not inconsistent with this opinion.

Notes, Comments, and Questions 

When the Court decided Riley v. California in 2014, it considered facts about a “container” that would have been unimaginable in 1973. Just a few decades ago, no arrestee had in his pocket a mini-computer full of private data, much less one capable of connecting to even more powerful computers with vast repositories of additional private information. Today, most arrestees carry such devices. The question before the Court was whether the rule from Robinson allows police to obtain data from a mobile phone found during a search incident to lawful arrest. 


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