Course: Introduction / Procedural Law
An Ex Post Facto Law is an unconstitutional type of statute that criminalizes an act after the act has occurred.
An ex post facto law, which is also known as a retroactive law, is a law that is enacted after an event has occurred and punishes individuals for committing an act that was not a crime at the time of the act. This type of law is prohibited by the Constitution of the United States.
The purpose of the prohibition is to ensure that individuals are not punished for actions that were legal at the time they were committed. This principle is based on the idea that people should have fair warning of what constitutes a crime, so they can avoid violating the law. The prohibition also ensures that lawmakers cannot change the rules after the fact to unfairly punish individuals or target specific groups of people.
A retroactive law can take many different forms. For example, a law that retroactively criminalizes an act that was not a crime when committed is classified as such. Additionally, a law that retroactively increases the punishment for a crime that was already committed is also prohibited. Finally, a law that retroactively changes the rules of evidence in a criminal trial is also prohibited as well.
The prohibition on ex post facto laws applies to both the federal government and state governments. The Supreme Court has interpreted the prohibition broadly and has struck down many laws that violate it. In general, the Court has held that a law violates the prohibition if it either criminalizes conduct that was legal at the time it was committed, increases the punishment for a crime that was already committed, or alters the rules of evidence in a way that affects a defendant’s rights.
One famous case that addressed the issue of ex post facto laws is Calder v. Bull (1798). In that case, the Supreme Court held that the ex post facto prohibition did not apply to laws that did not involve criminal penalties. However, the Court also emphasized that the prohibition was an important principle of justice and should be applied whenever possible.
Another important case that addressed the issue of ex post facto laws is Carmell v. Texas (2000). In that case, the Supreme Court held that a law that retroactively changed the rules of evidence in a criminal trial violated the ex post facto prohibition. The Court reasoned that the law unfairly affected the defendant’s rights and violated the fundamental principle of fairness in the criminal justice system.
Learn More
On This Site
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- Criminal Justice | Section 3.2: Substantive Criminal Law
- Criminal Law » Section 1.2 » Ex Post Facto Laws
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On Other sites
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- “Ex Post Facto Laws.” West’s Encyclopedia of American Law.
- “Retroactivity of Judicial Decisions.” Encyclopedia of the American Constitution.
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[ Glossary ]
Last Modified: 04/09/2023