## Facts

- Federal law criminalizes possession of an unregistered “firearm,” including a “machinegun,” defined as a weapon that shoots automatically more than one shot by a single trigger pull.
- Harold E. Staples III possessed an AR-15 rifle that, after inspection, contained several M-16 parts and had been altered so a selector could rotate to an automatic position.
- Government testing showed the rifle fired more than one shot with a single pull of the trigger.
- The rifle was not registered in the National Firearms Registration and Transfer Record.
- Staples testified the rifle had never fired automatically while he possessed it and claimed he did not know it could fire automatically.

## Issues

1. Whether a conviction for possessing an unregistered machinegun under 26 U.S.C. § 5861(d) requires proof the defendant knew the weapon had the characteristics that made it a machinegun.

## Decision

- The Supreme Court reversed by a 7–2 vote.
- The Court held the Government must prove beyond a reasonable doubt that the defendant knew the firearm had the features that brought it within the statutory definition of a machinegun.
- The Court rejected treating § 5861(d) as a strict-liability “public welfare” offense based solely on statutory silence.

## Legal Principles

- When a federal criminal statute is silent on mens rea, courts generally presume Congress intended some mental-state requirement absent a clear indication to dispense with it.
- For § 5861(d), the required mens rea concerns knowledge of the weapon’s factual characteristics (automatic-fire capability), not knowledge of the registration requirement or the statute’s legal terms.
- The “public welfare offense” inference of strict liability is disfavored where the regulated item is commonly possessed for lawful purposes and the statute imposes severe felony penalties.

## Conclusion

A defendant may not be convicted under 26 U.S.C. § 5861(d) for possessing an unregistered machinegun unless the Government proves the defendant knew the weapon had the characteristics—specifically automatic-fire capability—that made it a machinegun under federal law.


Staples v. United States, 511 U.S. 600 (1994)