In the case of Mathis v. United States, Richard Mathis was convicted in Iowa for burglary and later federally for being a felon in possession of a firearm. Under the Armed Career Criminal Act (ACCA), his sentence was enhanced due to prior convictions including five burglaries in Iowa. However, Mathis argued that these should not count as they were broader than generic burglary definitions under ACCA because it included locations like "any building, structure, [or] land, water or air vehicle." The Supreme Court ruled 5-3 in favor of Mathis stating that sentencing courts may look only to statutory elements - facts necessarily proved at trial - when assessing prior convictions under ACCA's force clause but not to underlying facts or documents unless alternative elements are involved which effectively create different crimes altogether. As such, since Iowa’s law defined burglary more broadly than did federal law by omitting an element of the crime rather than creating alternatives; it could not be used as predicate offense enhancing his sentence.

In the dissenting opinion for Mathis v. United States, Justice Breyer argued that the majority's approach was too rigid and complex. He contended that it would be more practical to consider whether state law defines crimes in a manner similar enough to generic offenses, rather than focusing on elements versus means of committing an offense. This approach would allow courts to use a common-sense evaluation of state laws instead of engaging in difficult legal analysis about distinctions between elements and means. Furthermore, he pointed out that this method has been used successfully by federal judges for years without causing significant problems or confusion. Ultimately, Justice Breyer believed the majority’s decision unnecessarily complicated matters and could lead to unjust results.