Knowles v. Iowa Case Brief

Why is the case important?

A police officer pulled over a speeder, issued a citation rather than arrest, and then searched the speeder’s car, finding drugs. The search was authorized by Iowa law even though there was no arrest.

Facts of the case

“After stopping him for speeding, an Iowa police officer issued Patrick Knowles a citation and conducted a full search of his car without probable cause or Knowles’ consent. When his search turned up a “”pot pipe”” and some marijuana, the officer arrested Knowles on state drug charges. Knowles challenged these on grounds that because he was not arrested at any time prior to the search, the search was unconstitutional. On appeal from consecutive adverse rulings in lower courts, the Supreme Court granted Knowles certiorari.”


Whether issuing a citation or similar such . . . procedure authorizes the officer, consistently with the Fourth Amendment, to conduct a full search of the car.


No. The court cited 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. The court concluded that neither of these rationales . . . are sufficient. For the former, the court reasoned that a routine traffic stop . . . is a relatively brief encounter. For the latter, the court argued that once the respondent was issued a citation all the evidence necessary to prosecute that offense has been obtained. No further evidence was going to be found either on the person of the offender or in the passenger compartment of the car.


“The Supreme Court of the  United States reversed and remanded the case for further proceedings. The Court held that the issuance of the citation did not authorize the officer, consistently with the Fourth Amendment, to conduct a full search of the car. The Court observed that neither of the two historical exceptions for the “”search incident to arrest”” exception was sufficient to justify the search. First, the threat to officer safety from issuing a traffic citation was a good deal less than in the case of a custodial arrest. Concern for safety during a routine traffic stop did not by itself justify the intrusion attending a full field-type search. Second, the need to discover and preserve evidence did not exist, as once Knowles was stopped for speeding and issued a citation, all evidence necessary to prosecute that offense had been obtained.”

  • Case Brief: 1998
  • Petitioner: Knowles
  • Respondent: Iowa
  • Decided by: Rehnquist Court

Citation: 525 US 113 (1998)
Argued: Nov 3, 1998
Decided: Dec 8, 1998