US Supreme Court Knowles v. Iowa 97-7597

Decided December 8, 1998.

   Knowles was stopped for speeding, in Iowa.  The law in Iowa authorized police to make a full custodial arrest for traffic offenses, or to simply issue a traffic ticket.  The law in Iowa also specified that if an officer chose to issue a traffic ticket rather than make an arrest, this would not diminish their authority to conduct an "otherwise lawful search."

   So Knowles was issued a ticket for speeding, and the officer conducted a "search incident to citation" of the car, discovering weed and a pot pipe.  Knowles was then arrested for real, and later convicted.  He appealed his conviction.  The US Supreme Court explained that the reasoning for the incident to arrest exception to the warrant requirement is twofold: 1- to protect the officer by allowing him to disarm his prisoner, and 2- to preserve evidence for later use at trial.  The court held that these justifications do not apply to issuing citations to the same extent that they do to making arrests, so they don't really merit an exception to the warrant requirement here.  The court noted that in cases where there is a heightened concern for safety, there are other doctrines that justify a search (but those didn't apply to this stop, either).

   Iowa's "search incident to citation" law was held to violate the 4th amendment, the evidence was suppressed, and Knowles' conviction was reversed.