You have a constitutional right to privacy, and this includes when you are driving your vehicle. While Fourth Amendment protections were drafted before the time of motor vehicles, the law still applies to this area as well. However, it is important to remember that you have a lower expectation of privacy in terms of your vehicle.
That being said, the police cannot simply search your vehicle because they feel like it. Unless they have a valid search warrant, then they are only permitted to carry out a search in the following circumstances.
If you let them
When an officer tells you that they would like to search your vehicle, you may think that you have no choice. This is a common reaction, and you may step out of the vehicle when requested and tell them to go ahead with the search. After all, you have nothing to hide. This is most likely not in your best interests though. What if someone else has left something that’s potentially incriminating in the vehicle without you realizing it?
A linked offense
If you have been arrested for possessing an illegal firearm or drugs, then officers may be entitled to search your vehicle if they have probable cause to believe that they are in danger or if more drugs are in the car.
Typically, without your consent, officers must have probable cause that other criminal evidence is within your vehicle before they carry out a search. If you have been arrested and believe that this was the result of an unlawful search, seeking some legal guidance will help you to build a defense.