Courts and commentators are increasingly concerned about police misconduct—searches and seizures that fail to comply with Fourth Amendment protections. Current doctrine attempts to deter such misconduct with the threat of excluding unlawfully seized evidence. The remedy of exclusion is weak, however, in large part because judges only see cases in which the defendant obviously is guilty. Despite years of proposals, the alternative of money damages is largely unavailable. The problem is exacerbated because Fourth Amendment law is notoriously uncertain. The combination of these three factors results in ineffective deterrence of Fourth Amendment violations. We propose to replace the failed deterrence model with a stringent ex ante warrant requirement. We make a novel case for warrants based on findings from the social sciences. The Court, rather than continuously weakening the warrant requirement, should reverse course and set warrants as the centerpiece of the Fourth Amendment.