What is the test for arrest under the fourth amendment?

The fourth amendment permits police to detain an individual only if they have an articulable and reasonable suspicion that the individual has committed or is about to commit a crime. United States v. Woods, 720 F.2d 1022, 1026 (9th Cir.1983). To arrest an individual, police need more than a reasonable suspicion; they must have probable cause. Probable cause to arrest exists when "under the totality of the circumstances known to the arresting officers, a prudent person would have concluded that there was a fair probability that [the defendant] had committed a crime." United States v. Smith, 790 F.2d 789, 792 (9th Cir.1986).