The Fourth Amendment requires that a warrantless arrest be based on probable cause. Amendment Four to the Constitution was ratified on December 15, 1791.It protects the American people from unreasonable searches and seizures. The probable cause must be used to gain a search warrant. The Constitution and 4th Amendment protects many types of unreasonable searches and seizures, however, it does not protect against things left out on the open. 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. Learn about the Fourth Amendment's requirements for probable cause in searches and seizures. A seizure that is lawful at its inception can violate the. It is often vague and unclear as to when probable cause exists. Probable cause in violation his Fourth Amendment rights.