Some state legislatures—and the United States Congress—have enacted so-called three-strikes laws (or three strikes, you’re out laws) to help law enforcement deal with violent repeat offenders—sometimes called persistent offenders, or prior and persistent offenders. The federal three-strikes law is a statute—also known as the Violent Crime Control Act—located in the United States Code at 18 U.S.C. §3559(c).

Under the federal three-strikes law, a person who is convicted in federal court of a serious violent felony and who has previously been convicted (in state or federal court) of (1) two or more serious violent felonies, or (2) one or more serious violent felonies and one or more serious drug offenses—will receive a mandatory sentence of life imprisonment.

Under the federal three-strikes law, serious violent felonies generally include federal or state offenses of (1) murder; (2) manslaughter (other than involuntary manslaughter); (3) assault with intent to commit murder; (4) assault with intent to commit rape; (5) sexual abuse and aggravated sexual abuse; (6) abusive sexual contact; (7) kidnapping; (8) aircraft piracy; (9) robbery; (10) carjacking; (11) extortion; (12) arson; (13) illegal firearms use; (14) illegal firearms possession; (15) attempt, conspiracy, or solicitation to commit any of these criminal offenses; and (16) any other offense punishable by a maximum term of imprisonment of 10 years or more that has as an element the use, attempted use, or threatened use of physical force against another person, or that involves a substantial risk that physical force against another person may be used in the course of committing the offense.

Three-strikes laws enacted by state legislatures vary from state to state—including what constitutes a strike offense—and are generally located in a state’s statutes—often in the penal or criminal code.

In Illinois, the three-strikes law is not as stringent as in some other states, and it does not automatically impose a life sentence for a third felony conviction. However, Illinois does have a version of a habitual criminal statute which can lead to increased penalties for repeat offenders. Under Illinois law, a person convicted of a third felony may be classified as a 'Class X' offender, which carries a mandatory minimum prison sentence of 6 to 30 years, depending on the specific crime and circumstances. This is not a mandatory life sentence, but it does reflect the state's intention to impose harsher penalties on repeat offenders. The federal three-strikes law, as outlined in 18 U.S.C. §3559(c), mandates a life sentence for certain repeat offenders who are convicted in federal court of a serious violent felony, provided they have two or more previous convictions for serious violent felonies or serious drug offenses. The list of serious violent felonies includes a range of offenses such as murder, sexual abuse, kidnapping, and robbery, among others. It's important to note that the federal law would apply to cases prosecuted in federal court, which may include offenses that cross state lines or violate federal law.