Putting Probability Back into Probable Cause
Social Science Research Network
When deciding whether a baseball player is likely to get a hit, we look at his history of success at the plate. When deciding whether to listen to the advice of a stock analyst, we look at whether the prices of her past recommendations rose or fell. But when police officers claim that they have probable cause to believe a certain location contains evidence of a crime, we do not look at whether they have been right or wrong when they have made the same claim in the past. This is a mistake.
... is a mistake. Law-enforcement-search success rates vary widely, even when the same legal standard applies. Searches pursuant to warrants issued on a probablecause standard recover evidence at very high rates, usually exceeding 80%. By contrast, warrantless searches, even when officers allege they have probable cause, succeed at far lower rates, recovering evidence as infrequently as 12% of the time. Similarly, some officers are far more successful than others when they conduct probable-cause searches. Some almost never recover evidence; some almost always do. What role should these different success rates play in probable-cause analysis? The current answer is none. Judges are not presented with the success rates of the law enforcement officers who appear before them. I argue that law enforcement should be forced to present success-rate data to judges when making probable-cause claims and judges should be allowed to consider the data when deciding whether to issue a warrant or approve a previously conducted search. These success rates capture information not currently analyzed in the search process and their addition would improve the accuracy of probable-cause decisions. Most significantly, we would learn private information in the possession of law enforcement that is not currently presented to judges.