The Armed Career Criminal Act of 1984’s definition of “violent felony” as an offense that “involves conduct that presents a serious potential risk of physical injury to another” is unconstitutionally vague. Johnson was convicted in federal court of being a felon in possession of a gun. The court sentenced Johnson to a 15-year prison term under the Armed Career Criminal Act of 1984, which provides that a defendant who has previously been convicted of three or more “violent felonies” is subject to an increased prison sentence. The district court had concluded that a prior state conviction qualified as a violent felony under the “residual clause” of the Act, which provides that an offense that “involves conduct that presents a serious potential risk of physical injury to another” is a violent felony (18 U.S.C. § 924(e)(2)(B)). Johnson’s challenge to his sentence was rejected by the Eighth Circuit. The U.S. Supreme Court granted certiorari. Held: Reversed. The Fifth Amendment to the U.S. Constitution prohibits the taking of a person’s liberty under a criminal law that is so vague it fails to provide adequate notice of the conduct it proscribes or allows for arbitrary enforcement. It applies not only to statutes defining elements of crimes, but also to statutes prescribing sentences. In deciding whether the residual clause covers a crime, a court is required to picture the kind of conduct that the crime involves in “the ordinary case” and to judge whether that abstraction presents a serious risk of physical injury. Here, the Court concluded that this wide-ranging inquiry “both denies fair notice to defendants and invites arbitrary enforcement by judges,” thereby denying due process. There is uncertainty about how to estimate the risk because the assessment is tied to a judicially imagined “ordinary case,” not real-world facts or statutory elements. There is also uncertainty about how much risk it takes for a crime to qualify as a violent felony. The Court overturned its contrary holdings in James v. United States (2007) 550 U.S. 192, and Sykes v. United States (2011) 564 U.S. 1.