The simple answer is, YES! The police can always search you. The real question is whether they can use what they find against you in court. Generally speaking, the U.S. Constitution and the Supreme Court have clearly said that warrantless searches are unconstitutional and any evidence found during an unconstitutional search shall be excluded as evidence in criminal proceedings. There are a few exceptions to this rule.
The first exception is if you give the police consent to search your person, your vehicle, or your home. This consent must be clear, but they can take something as small as a head nod as consent. This gets to be a very complex issue when you bring language barriers into play. The safest bet is to just say “NO” to any and all requests to search.
The second exception is when the police have probable cause. Probable cause means that there is sufficient reason based upon known facts to believe a crime has been committed or that certain property is connected with a crime. The idea here is that it may take too long to obtain a search warrant, and evidence may be removed or destroyed, so the Supreme Court allows police officers to search a person or a vehicle if a warrant would have been given anyway. Probable cause can be deduced by police observations, such as the smell of alcohol, the smell of marijuana, or seeing contraband (drugs or a gun) in plain view. The best way of avoiding this type of search is by not giving them a reason to stop you.
The last exception we’ll discuss in this article is an inventory search. This happens when your vehicle is impounded for towing by the police. It is an inventory of the contents of your vehicle. Any contraband they find can be used against you in a court of law. How can you avoid this? Make sure that you pull into a parking lot or private driveway. The police can only impound and tow your vehicle if it is a safety hazard, like on the roadway. If it is on private property, like a store or gas station parking lot, they cannot impound your vehicle and therefore any evidence they find as part of an inventory search is inadmissible in court.
We have only touched the surface of the issues surrounding search and seizure of evidence. This is just another reason to hire a lawyer who is well versed in the 4th Amendment to prevent the police from violating your Constitutional Rights.