What is Probable Cause? "Under the Fourth and Fourteenth Amendments, an arresting officer may, without a warrant search a person validly arrested.Under the Fourth Amendment, the police can conduct a search in two ways. The Fourth Amendment mandates that search warrants must describe with particularity the place to be searched and the persons or things to be seized. Since requests to search a vehicle normally are not part of the mission of a stop, seeking consent risks unlawfully extending the stop. The Fourth Amendment to the U.S. Constitution provides the constitutional grounds for excluding evidence obtained through an illegal search and seizure. The Fourth Amendment requires the government to obtain a warrant based on probable cause to conduct a legal search and seizure. Probable cause is present when the police officer has a reasonable belief in the guilt of the suspect based on the facts and information prior to the arrest. The Fourth Amendment of the U.S. Constitution protects people from unreasonable searches or seizures or the issuance of a search warrant without probable cause. In the second group of cases, law enforcement officers have probable cause.