Fourth Amendment: Probable Cause and Reasonable Suspicion

The Fourth Amendment provides that “no warrants shall issue, but upon probable cause.” Accordingly, warrants (and the searches that followed in the wake of their issuance) have been challenged on the ground that police did not provide sufficient evidence when obtaining the warrants from judges. In addition, the Court has held that in several common situations, police may conduct searches and seizures without a warrant, but only with probable cause. In Illinois v. Gates, the Court set forth a new standard for when an informant’s tip provides probable cause to justify a search or arrest.