“Well my glove compartment is locked so is the trunk and the back
And I know my rights so you gon’ need a warrant for that,” – 99 Problems by Jay-Z
The Fourth Amendment is the section of the U.S. Constitution that protects the public from unreasonable searches and seizures.
Warrantless searches are presumed to be unconstitutional; however, the Supreme Court of the United States has carved out many exceptions.
One of these exceptions is the automobile exception. The Supreme Court has held that due to the mobile nature of motor vehicles and the fact that they are heavily regulated (in addition to the fact that they are driven on public streets and highways), the police do not need a warrant to search your vehicle. Instead, they can proceed to search your vehicle based on probable cause. Probable cause is defined as sufficient information based on known facts and circumstances that would give a man of reasonable caution a belief that a crime has been or is being committed. There are other exceptions that allow warrantless searches such as a search incident to arrest or a limited search in the passenger compartment if the officer reasonably suspects the driver or passenger may be dangerous or have access to a weapon.
The issue arises when the warrant exception combines with the “plain view” rule. If the police see or smell something in plain view that gives them probable cause to believe a crime is being committed, they can then proceed to search the vehicle. An example is if the officer sees a weapon or illegal drugs in front of him on the car seat or floorboard, or if he smells a strong odor of marijuana. At that point, the officer can proceed to search the vehicle as the odor of marijuana provides probable cause that the driver or passenger is in possession of marijuana. The search will be legal as long as the areas searched are areas where evidence that relates to the suspected crime can be found. Closed containers can be searched if the officer has reason to believe he will find evidence of the crime in them, otherwise the search may be broader than what is legally authorized. Similarly, a search of the locked trunk would require probable cause to believe that evidence of the crime that is being investigated is contained in the trunk.
So if a person is stopped for a routine traffic infraction, and the officer then smells marijuana, he may ask to search the vehicle. If consent is given, the officer will perform the search and the search will be legal. If consent is withheld, the officer can then proceed to search the vehicle based on probable cause due to the plain odor of marijuana. But police usually prefer to get consent first, before they search, in case there is an issue as to whether there was enough facts to give them probable cause for the search. This is why many defense attorneys advise people to generally not consent to any searches. If it is later determined that the officer did not have sufficient facts to give him probable cause to search the vehicle, nor did he have consent from the occupant, a strong argument that the evidence should be suppressed could be brought through a pre-trial motion that could suppress the evidence on the basis of an illegal search.