by Paul J. Larkin, Jr.
A millennium ago, the criminal law was simple. If you knew the Decalogue, you knew what not to do: don't murder, steal, or lie. As a result, the law did not exonerate someone who claimed to believe that what he did was not a crime, since no one could reasonably believe that those immoral actions were not also illegal. Today, however, the criminal law has expanded to Brobdingnagian proportions. There are approximately 4,500 federal crimes alone. Atop that, use of administrative agencies to define criminal statutes (or their terms) exacerbates the problem. Congress may use a broadly defined term (e.g., "solid waste") in a statute (e.g., the Resource Conservation and Recovery Act) that delegates to an agency (e.g., the EPA) the power to define its terms (e.g., "hazardous waste") by creating a list of specific examples (e.g., "listed hazardous wastes") or by specifying exemptions (e.g., "recyclable materials"). The result is that there are perhaps 300,000 potentially relevant regulations. No one--no law enforcement officer, no lawyer, no law professor, no judge--could honestly claim to know them all.
A reasonable mistake defense avoids the risk that a morally blameless person could be convicted of conduct that no reasonable person would have known was a crime. Even a child knows the inherent unfairness of being punished for conduct that no one, not even an adult, would reasonably have known was out of bounds. The simplest and most direct remedy, therefore, is to allow a person to prove that he made a mistake and that his mistake was reasonable.
A reasonable mistake defense does not pose the risk that rogues could manipulate it and escape justice. Some conduct is so well known as immoral and illegal that no one reasonably could claim ignorance of the law as an excuse. Murder, manslaughter, rape, mayhem, robbery, burglary, arson, and larceny were crimes at common law and have been outlawed by state and federal criminal codes ever since. Kidnapping, possession of heroin, and the like are modern crimes everyone knows or should know. No one could reasonably claim ignorance that such conduct, or even analogous behavior, is prohibited. A reasonableness requirement would impose a sensible limitation on a Mistake of Law Defense and would go a long way toward eliminating the concern that scallywags will wriggle out of responsibility for conduct that any reasonable person would have known is a crime.