Mistake of Law

A misconception that occurs when a person with complete knowledge of the facts reaches an erroneous conclusion as to their legal effect; an incorrect opinion or inference, arising from a flawed evaluation of the facts.

Generally, a mistaken belief about a law is no defense to a violation of that law. All persons are presumed to know and understand the law, except minors, persons who lack mental capacity to contract with others, and, in criminal cases, persons who are insane. There are, however, a few other rare exceptions to this general rule.

A mistake of law may be helpful to criminal defendants facing prosecution for a specific-intent crime. A specific-intent crime requires that a defendant act with a criminal intent beyond the general intent required to commit the act. Murder, for example, is a specific-intent crime. The prosecution must show that the defendant specifically intended to kill the victim without justification. Manslaughter, conversely, requires only a showing that the defendant intended to do those actions that caused the death. If a defendant is charged with a specific-intent crime, the defendant's reasonable mistaken belief about the law may reduce the defendant's criminal liability.

For example, assume that a defendant is accused of robbing another person. Assume further that the defendant was actually trying to retrieve money that the alleged victim owed to the defendant. A court may hold that the defendant mistakenly believed that the law allows Self-Help in such situations and that the mistaken belief about the law negated the Specific Intent required for the crime. That is, the defendant did not have the specific intent to gain control over the property of another person. Generally, a mistake of law is helpful to criminal defendants only in specific-intent cases. For general-intent and Strict Liability crimes, a mistake of law is no defense.

There are other exceptions to the general rule that ignorance of the law is no excuse. If a defendant relied on a statute that permitted a certain act and the act is later made illegal, the defendant cannot be prosecuted. This applies to general-intent and strict liability crimes as well as specific-intent crimes. If a defendant reasonably relies on a judicial decision, an opinion, or a judgment that is later reversed, the reversal does not retroactively make a related act illegal. Similarly, if a defendant acts with reasonable reliance on an official statement of law in an administrative order or from an official interpretation by a public officer or government agency, the defendant may use the mistake-of-law defense. Mistaken advice from an attorney, however, does not create a mistake-of-law defense.

Further readings

"Criminal Law and Procedure." 1994. SMH Bar Review.

Kionka, Edward J. 1988. Torts. St. Paul, Minn.: West.