Duhaime's Law Dictionary

Rule of Lenity Definition:

A rule of construction of statutes: that criminal statute ambiguities are resolved in favor of the defendant or accused.

In US v Gonzalez-Mendez, Justice Wallace of the United States Court of Appeal noted the following:

"Under the rule (of lenity), we construe ambiguities in criminal statutes in favor of defendants. However, we resort to the rule of lenity only if the statute is truly ambiguous."

In US v Bass, Justice Marshall of the United States Supreme Court expressed the rule as follows:

"Ambiguity concerning the ambit of criminal statutes should be resolved in favor of lenity."

In Bifulco, Justice Blackmun of the US Supreme Court adopted these words:

"This policy of lenity means that the Court will not interpret a federal criminal statute so as to increase the penalty that it places on an individual when such an interpretation can be based on no more than a guess as to what Congress intended.

"The Court has emphasized that the touchstone of the rule of lenity is statutory ambiguity. Where Congress has manifested its intention, we may not manufacture ambiguity in order to defeat that intent."


  • Bifulco v United States 477 US 381 (1980)
  • US v Bass 404 US 336 (1971)
  • US v Gonzalez-Mendez 150 F. 3d 1058 (1998, United States Court of Appeals)

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