Staples bought a used gun.
Turns out it was an automatic machine-gun.
Possession of the weapon was
a violation of the National Firearms Act.
The gun had a metal thingee
that prevented it from firing automatically, but someone had filed it
Staples claimed he had no
idea that the gun could fire automatically.
At Trial, Staples requested a
jury instruction that he couldn't be found guilty unless there was proof
that he knew the gun could fire automatically. The Trial Judge refused to
issue the instruction.
Looking at the Statute, the
judge found that it did not require knowledge (aka mens rea), but that it was a strict liability crime.
The Trial Court convicted
Staples of possessing an illegal firearm. He appealed.
The Appellate Court affirmed.
The US Supreme Court reversed.
The US Supreme Court noted
that the Statue was silent on whether or not mens rea was a required element.
The Court found that strict
liability for criminal offenses is
generally disfavored, and the courts are to assume that there is a mens
rea requirement unless the Statute
explicitly says there isn't.
The prosecutor argued that
"public welfare" and "regulatory" offenses generally
do have strict liability (for
example, parking tickets), and that this Statute was similar, because
people running around machine guns was a threat to public welfare.
Many crimes involving
"possession of dangerous devices of a character that places the
possessor in responsible relation to a public danger" have strict
The Court rejected that
argument because the 2nd Amendment and the historical common law have granted
unfettered rights to gun owners.
Conversely, the Court
noted that if Staples had been arrested for possessing a grenade, then
that would be a strict liability