Taking Mistakes Seriously

Abstract

There are two very different mistake doctrines in the law. The common law doctrine that ignorance of the law is no excuse gives no weight to reasonable, good faith mistakes insofar as criminal liability is concerned. By contrast, three related lines of decisions — the reasonable-mistake, qualified-immunity, and harmless-error doctrines — express great willingness to overlook reasonable, good faith mistakes that police officers, prosecutors, and judges make. That discrimination is unwarranted. There is no good reason to treat private parties systematically worse than public officials in this regard. The courts have created these competing lines of decisions, and they, or Congress, should eliminate that discrimination by extending to members of the public the same grace that they offer to every government official. The most straightforward way to remedy this problem is to recognize a mistake-of-law defense in the substantive criminal law.

Keywords: Mistake of law, ignorance of the law, reasonable mistake exception to the exclusionary rule, qualified immunity, harmless error doctrine