The Fourth Amendment to the U.S. Constitution prohibits unlawful search and seizures. This means that if law enforcement officers search your vehicle without having a valid reason or your permission, then your constitutional rights have been violated.
The courts will usually give an officer a bit more leeway when it comes to searching a car than searching a home. This is because people have a lower expectation of privacy when they are driving a vehicle. In addition, public safety concerns also add to the exception, such as speeding or driving under the influence.
Police can search your vehicle, though, under the following circumstances:
-- An officer has a search warrant for your vehicle.
-- The search of your vehicle is related to your arrest.
-- An officer believes that searching your vehicle is necessary for his or her own protection.
-- An officer believes there is evidence relating to a crime in your car.
-- You give the officer consent to search your vehicle.
If an officer asks to search your vehicle and you tell him or her no, then evidence he or she obtains may not be able to be used against you in court. However, if the officer has probable cause to believe that there is evidence in your vehicle related to a crime, then he or she can search your vehicle.
Should an officer see evidence of a crime in plain view, then he or she can seize that evidence and search your vehicle. This includes sensory evidence -- such as a drug dog detecting the smell of drugs or someone hollering for help from your trunk.
Your attorney can provide more information on whether a search of your vehicle is legal.
Source: FindLaw, "When Can the Police Search Your Car?," accessed March 31, 2016