Criminal Procedure

An example of this principle may be seen with the so-called automobile exception to the Constitution's search-warrant requirement. Under the automobile exception, states may allow the warrantless search of an automobile, except for the trunk, if the police officer reasonably believes that the vehicle holds evidence of a crime. The U.S. Supreme Court has determined that this exception is not a violation of the Fourth Amendment because drivers have a "reduced expectation of privacy" and because a vehicle is inherently mobile. This reduced expectation of privacy also allows police officers with PROBABLE CAUSE to search a car to inspect drivers' and passengers' belongings that are capable of concealing the object of the search, even if there is no proof that the driver and passenger were engaged in a common enterprise. Wyoming v. Houghton, 526 U.S. 295, 119 S. Ct. 1297, 143 L. Ed. 2d 408 (1999).

However, states are not required to adopt the automobile exception. The New Hampshire Supreme Court, for example, ruled that all warrantless searches are unreasonable except for a group of well-defined such searches, and this group does not include warrantless AUTOMOBILE SEARCHES (State v. Sterndale, 139 N.H. 445, 656 A.2d 409 [1995]). Thus, in New Hampshire, a police officer may not base the warrantless search of a vehicle on the mere fact that the place to be searched is a vehicle. New Hampshire, therefore, provides expanded protections under the Fourth Amendment.

Conversely, a state may not allow the search of any vehicle without reasonable suspicion. A vehicle search that is conducted in the absence of reasonable suspicion would be an infringement of guaranteed Fourth Amendment protection, and a court would strike down such an infringement as unconstitutional. A state law may not diminish the scope of the automobile exception by authorizing a warrantless search of an entire vehicle following a traffic stop in which the driver is issued a citation for speeding. Although law enforcement may conduct a full vehicle search if the defendant is formally arrested, the issuance of a traffic citation does not justify the considerably greater intrusion of a full-fledged search. Knowles v. Iowa, 525 U.S. 113, 119 S. Ct. 484, 142 L. Ed. 2d 492 (1998)