You can’t question a secret you haven’t been told. The criminal legal system depends on fair and open proceedings to expose and regulate unlawful and unconstitutional police conduct through the courts. If police can use claims of secrecy to systematically thwart criminal defendants' access to evidence, judicial review will fail. And yet that is exactly what is happening under a common-law doctrine called the “law enforcement privilege.” The privilege empowers police and prosecutors to rely on the results of secret investigative methods while withholding information from the defense about how those methods work. It risks perpetuating unconstitutional conduct, enabling wrongful convictions, and rendering Fourth Amendment, Sixth Amendment, Brady, and statutory discovery laws moot. At the same time, it has a non-frivolous policy rationale. If all police investigative methods were public information, then more people committing crimes could evade detection.

How can a better balance be struck? This Article argues that cur-rent law enforcement privilege doctrine creates a dangerously boundless police secrecy power because of a subtle conceptual collapse: the policy rationale itself is mistakenly used as the test for assessing claims of privilege. The Article recommends that courts instead evaluate privilege claims by reference to the marginal risk of leaking posed by in-court disclosure. Specifically, judges should demand to know what conditions law enforcement previously imposed on access to the information. The answer to that question can be adjudicated publicly without jeopardizing a legitimate privilege claim and will help judges detect mistaken, exaggerated, pretextual, or fraudulent claims to the privilege. Further, even when law enforcement has taken care with the information, if a court-ordered protective order can match or exceed the safeguards that law enforcement itself previously maintained, then judges should default to ordering disclosure. The Article concludes by suggesting a theory of the role of confidentiality in privilege law as a whole.