Ex Post Facto

The term “ex post facto” translates to “out of the aftermath,” or “from a thing done afterward.” In the legal world, the term refers to the punishing of an act that was once legal, but is now criminal. For example, ex post facto laws can either create new penalties for a particular action or extend sentences already issued. To explore this concept, consider the following ex post facto definition.

Definition of Ex Post Facto


  1. A type of law that criminalizes conduct that once was legal.



Ex Post Facto Laws

Ex post facto laws are laws that criminalize conduct that was previously legal. These laws can also make punishments that were already in place more severe. For example, ex post facto laws may add years to a defendant’s sentence.

There are two clauses in the U.S. Constitution that prohibit ex post facto laws. Specifically, Article 1, Section 9 dictates that Congress cannot pass any ex post facto laws, and Article 1, Section 10 explains the same rule for the states. This is only one of the few restrictions the Constitution makes on both the state and federal governments. In fact, Thomas Jefferson called ex post facto laws as “equally unjust” in civil cases as it is in criminal. However, the Constitution does not prohibit all laws that apply retroactively.

Adam Walsh Child Protection and Safety Act

In July of 2006, President George W. Bush signed the Adam Walsh Child Protection and Safety Act. The Act received its name in honor of a young victim who was murdered after his abduction from a mall in Florida. Otherwise referred to as the “Walsh Act,” this law designates three “tiers,” or categories, of sex offenders, grouping them by the severity of their crimes.

The Three Tiers

The most serious of these categories, or tiers, is the third tier. Sex offenders that belong to this tier must update their location every three months, and they register for life. Sex offenders who belong to the second tier must update their location every six months, and they register for 25 years. Those belonging to the first tier must update their location once a year and register for 15 years. Failure to comply with these terms for any tier, regardless of severity, is a felony.

The Walsh Act is also the reason why a sexual offender registry exists today. In order to compile the registry, states must submit identifying information about each offender to the database, such as the offender’s:

  • Name and address
  • Date of birth
  • Place of employment
  • A photo of the offender

Ex Post Facto Example Involving Child Abuse

An example of ex post facto comes from the case of Stogner v. California, which the Supreme Court heard in June of 2003. Here, Marion Stogner, charged with sex-related child abuse from the period of 1955 to 1973, was indicted in 1998. He came to the authorities’ attention when his daughters reported, in a connected investigation, that Stogner had repeatedly abused them while they were under the age of 14 years old.

In 1993, the state of California passed a new statute of limitations regarding prosecution for sex-related child abuse. Specifically, the law allowed the prosecution of a person who otherwise would not have been due to the statute expiring. However, for this to occur, the prosecution must indict the defendant within one year of the victim’s report.

During the time Stogner allegedly committed the crimes at issue, the statute of limitations in the state of California for these crimes was three years. Stogner moved to dismiss the charges against him, arguing that the ex post facto clause of the Constitution prohibited the new statute. Further, he argued that the new statute impeded upon his rights to due process.

Trial and Appeal

Upon the conclusion of his trial, the trial court agreed with Stogner that the ex facto clause prohibits the revival of a prosecution that once was time-barred. However, they dismissed his motion for dismissal. On appeal, the California Court of Appeal reversed the trial court’s decision on the former and confirmed the court on the latter.

Stogner then appealed to the U.S. Supreme Court, who agreed to hear the case. The Court then had to decide whether the ex post facto clause prohibited California from retroactively extending the statute of limitations on sexual abuse cases involving minors.

Supreme Court Decision

Ultimately – and perhaps surprisingly – the Court sided with Stogner on this one. In a 5-4 decision, the Court ruled that yes, California had violated the ex post facto law when it tried to revive an otherwise time-barred action. The Court’s reasoning was that California’s statute did exactly what the ex post facto clause tries to prevent: imposed punishment on an individual who was not liable as defined by the law.

Specifically, the Court wrote:

“A law enacted after expiration of a previously applicable limitations period violates the Ex Post Facto Clause when it is applied to revive a previously time-barred prosecution. California’s law extends the time in which prosecution is allowed, authorizes prosecutions that the passage of time has previously barred, and was enacted after prior limitations periods for Stogner’s alleged offenses had expired. Such features produce the kind of retroactivity that the Constitution forbids.

First, the law threatens the kinds of harm that the Clause seeks to avoid, for the Clause protects liberty by preventing governments from enacting statutes with ‘manifestly unjust and oppressive’ retroactive effects. (Citation omitted.)

Second, the law falls literally within the categorical descriptions of ex post facto laws that Justice Chase set forth more than 200 years ago in Calder v. Bull, which this Court has recognized as an authoritative account of the Clause’s scope (citation omitted). It falls within the second category, which Justice Chase understood to include a new law that inflicts punishments where the party was not, by law, liable to any punishment. Third, numerous legislators, courts, and commentators have long believed it well settled that the Clause forbids resurrection of a time-barred prosecution.”

Related Legal Terms and Issues

  • Defendant – A party against whom a lawsuit has been filed in civil court, or who has been accused of, or charged with, a crime or offense.
  • Due Process – The fundamental, constitutional right to fair legal proceedings in which all parties will be given notice of the proceedings, and have an opportunity to be heard.
  • Sex Offender – A person who commits a crime that is sexual in nature.
  • Statute Sex Offender of Limitations – A law that details the specific period within which a kind of legal action can be pursued.
  • Trial – A formal presentation of evidence before a judge and jury for the purpose of determining guilt or innocence in a criminal case, or to make a determination in a civil matter.