Kiel Robert Brennan-Marquez (New York University School of Law; Yale University - Information Society Project) has posted Plausible Cause on SSRN. Here is the abstract:
“Probable cause” is not about probability. It is about plausibility. To determine if an officer has the requisite suspicion to perform a search or seizure, what matters is not the statistical likelihood that a “person, house, paper or effect” is linked to criminal activity. What matters is whether criminal activity provides a convincing explanation of observed facts. For an inference to register as plausible, an observer must understand why the inference follows; she must be able to explain its relationship to observed facts. Probable inferences, by contrast, need not be explanatory. An inference can be probable—in a predictive sense, based on past trends—without a human observer understanding what makes it so.
In many cases, probability and plausibility overlap. An inference that is likely to be true (probability) will often explain observed facts (plausibility), and vice versa. But there is an important sub-set of cases in which the two properties pull apart, raising deep questions about the underpinning of Fourth Amendment suspicion: inferences generated by predictive algorithms. In this Article, I argue that casting suspicion in terms of plausibility, rather than probability, is both more consistent with established law and crucial to the Fourth Amendment’s normative integrity. Before law enforcement officials may intrude on private life, they must explain why they believe wrongdoing has occurred. This requirement serves two related goals. First, it facilitates governance; we cannot effectively regulate what we do not understand. Second, explanation-giving allows judges to consider the “other side of the story”—the innocent version of events that a suspect might offer on her own behalf—before warranting searches and seizures. I close by arguing that these virtues generalize beyond the Fourth Amendment. In a democracy, legitimacy is not measured solely by outcomes. The exercise of state power must be explained. And the explanations must be responsive to the democratic community writ large, and to the specific individuals whose interests are infringed.