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Probable Cause and Reasonable Suspicion: Totality Tests or Rigid Rules?

Since its decision more than thirty years ago in Illinois v. Gates, the Supreme Court has emphasized that the Fourth Amendment’s suspicion requirements—the probable cause required to arrest and search, the reasonable suspicion needed to stop and frisk—are totality‐of‐the‐circumstances tests. Gates overturned Supreme Court precedent that had held for nearly two decades that a tip did not give rise to probable cause absent evidence that the informant both (1) was honest and (2) had a reliable basis for her information. Rejecting this “rigid” two‐part test, the Gates Court stressed that probable cause is a “fluid,” “practical, common‐sense” concept that is “not readily, or even usefully, reduced to a neat set of legal rules.”

The Court has used similar language to explain the totality‐of‐the‐circumstances analysis applied when measuring the lower quantum of proof necessary to create reasonable suspicion. With the exception of one outlier—Illinois v. Wardlow, which articulated the sweeping rule that “[h]eadlong flight” in a “high crime area” constitutes reasonable suspicion—the Court has repeatedly recited the common‐sense, totality‐of‐the‐circumstances mantra when defining both probable cause and reasonable suspicion.

In two recent opinions, however, the Court has strayed from this path, leaning towards reliance on bright‐line rules to define probable cause and reasonable suspicion. Perhaps not surprisingly, these deviations have come in cases where a totality‐of‐the‐circumstances approach is more likely to favor criminal defendants. And both times, the tests that have emerged from the Court’s rulings have tended to oversimplify by exaggerating the reliability of the information used by the police. This essay examines the jurisprudential climate that produced these opinions and their potential repercussions.