Dyson (defendant) was a known drug dealer. Police received a tip from an informant that Dyson was carrying illegal drugs. The informant described the vehicle and gave police the license plate number. Police stopped and searched the vehicle. After finding drugs, the police arrested Dyson. Dyson was convicted at trial. Dyson appealed arguing that the search violated his Fourth Amendment rights. The Maryland Court of Special Appeals reversed Dyson’s convictions because it concluded that police could only conduct a constitutionally permissible warrantless vehicle search under exigent circumstances. The state of Maryland (plaintiff) appealed the ruling in state court, but was denied certiorari. The state appealed to the United States Supreme Court.