What is the primary condition under which police may search a vehicle without a warrant?

The primary condition under which police may search a vehicle without a warrant is when they have probable cause to believe that the vehicle contains contraband and it is mobile. This principle is rooted in the legal doctrine known as the "automobile exception" to the Fourth Amendment's warrant requirement.

The rationale behind this exception is that vehicles are inherently mobile, meaning evidence could be quickly moved or destroyed if officers were required to obtain a warrant first. If law enforcement officers observe circumstances that lead them to reasonably believe that a vehicle contains illegal items, such as drugs or stolen property, they can perform a search without obtaining a search warrant. This allows officers to act quickly to prevent the loss of evidence and to ensure public safety.

While the other choices present various circumstances that could lead to searches, they do not reflect the foundational legal criteria necessary for warrantless searches. For instance, while consent from the driver enables a search, probable cause specifically addresses situations that warrant immediate action due to the potential loss of evidence. Similarly, suspicion alone without concrete evidence does not provide sufficient legal justification for a warrantless search.