Search and Seizure - Probable Cause And Reasonable Suspicion

Once it has been established that an individual possesses a reasonable expectation of privacy in a place to be searched or a thing to be seized, the Fourth Amendment's protections take hold, and the question then becomes what are the nature of those protections. Police officers need no justification to stop someone on a public street and ask questions, and individuals are completely entitled to refuse to answer any such questions and go about their business. However, a police officer may only search people and places when the officer has probable cause or reasonable suspicion to suspect criminal activity.

"Probable cause" means that the officer must possess sufficiently trustworthy facts to believe that a crime has been committed. In some cases, an officer may need only a reasonable suspicion of criminal activity to conduct a limited search. Reasonable suspicion means that the officer has sufficient knowledge to believe that criminal activity is at hand. This level of knowledge is less than that of probable cause, so reasonable suspicion is usually used to justify a brief frisk in a public area or a traffic stop at roadside. To possess either probable cause or reasonable suspicion, an officer must be able to cite specific articulable facts to warrant the intrusion. Items related to suspected criminal activity found in a search may be taken, or seized, by the officer.