The motor vehicle exception was first established by the United States Supreme Court in 1925, in Carroll v. United States. The motor vehicle exception allows an officer to search a vehicle without a search warrant as long as he or she has probable cause to believe that evidence or contraband is located in the vehicle. The exception is based on the idea that there is a lower expectation of privacy in motor vehicles due to the regulations under which they operate. Additionally, the ease of mobility creates an inherent exigency to prevent the removal of evidence and contraband. In Pennsylvania v. Labron the U.S. Supreme Court, stated, "If a car is readily mobile and probable cause exists to believe it contains contraband, the Fourth Amendment permits the police to search the vehicle without more." The scope of the search is limited to only what area the officer has probable cause to search. This area can encompass the entire vehicle including the trunk. The motor vehicle exception, in addition to allowing officers to search the vehicle, allows officers to search any containers found inside the vehicle that could contain the evidence or contraband being searched for. The objects searched do not need to belong to the owner of the vehicle. In Wyoming v. Houghton, the U.S. Supreme Court ruled that the ownership of objects searched in the vehicle is irrelevant to the legitimacy of the search. Some states' constitutions require officers to show there was not enough time to obtain a warrant. With the exception of states with this requirement, an officer is not required to obtain a warrant even if it may be possible to do so. In United States v. Ludwig, the Tenth Circuit Court of Appeals found that a search warrant is not required even if there is little or no risk of the vehicle being driven off. The court stated, "f police have probable cause to search a car, they need not get a search warrant first even if they have time and opportunity." In United States v. Johns, the U.S. Supreme Court upheld a search of a vehicle that had been seized and was in police custody for three days prior to the search. The court stated, "A vehicle lawfully in police custody may be searched on the basis of probable cause to believe it contains contraband, and there is no requirement of exigent circumstances to justify such a warrantless search." The U.S. Supreme Court in California v. Carney found the motor vehicle exception to apply to a motor home. The court did however, make a distinction between readily mobile motor homes and parked mobile homes. A number of factors including, the home being elevated on blocks, whether the vehicle is licensed, and if it is connected to utilities determine if the motor vehicle exception applies. In United States v. Johns, the motor vehicle exception was applied to trucks. In United States v. Forrest it was applied to trailers pulled by trucks. United States v. Forrest applied the exception to boats and in United States v. Hill to house boats. In United States v. Nigro and United States v. Montgomery the motor vehicle exception was found to also include airplanes.
Development of the exception
The automobile exception has gone through five phases as marked by Supreme Court cases:
A. Early cases; Carroll v. United States to United States v. Di Re and the requirement of exigency
B. Chambers v. Maroney and the relaxing of exigency
C. Automobile exception first applied to containers in Arkansas v. Sanders
D. Probable cause and containers -- United States v. Ross
E. The clearer movement toward automobile—exigency
The vehicle exception does not include vehicles parked within private property where there is a reasonable expectation of privacy, which includes a home and its surrounding curtilage, defined by the Fourth Amendment, as determined in Collins v. Virginia. The Supreme Court also ruled in the 2017 case Byrd v. United States that the motor vehicle exception also includes to those driving rental vehicles even if the driver is not listed on the rental agreement.
