Prohibiting Ex Post Facto Laws

Instructor: Ashley Dugger

Ashley is an attorney. She has taught and written various introductory law courses.

The United States Constitution prohibits ex post facto laws. Ex post facto laws are retroactive, meaning they seek to penalize 'after the fact'. This lesson explains the constitutional prohibition on ex post facto laws.

Ex Post Facto Laws

Mr. Blue was convicted of burglary. At the time of his conviction, burglary carried a possible prison sentence of five years. Mr. Blue's sentencing was set for two weeks after his conviction. During that time, his state legislature passed a new law making the punishment for burglary a mandatory seven year prison sentence. When Mr. Blue is sentenced, the judge gives him the mandatory seven year prison sentence.

Mr. Blue thinks his sentence is unconstitutional. Is he right? He probably is! Let's look at why.

The new sentencing law, as applied to Mr. Blue, is an ex post facto law. 'Ex post facto' is a Latin term meaning 'from a thing done afterward.' An ex post facto law is one that works retroactively in an attempt to govern past actions. It's a law that makes an act criminal, even though the act was lawful when it was committed or it can be a law that inflicts a harsher punishment than was permitted when the act was committed.

The United States Constitution specifically prohibits ex post facto laws. The Constitution's Article 1, Section 9 prohibits ex post facto federal laws, and Article 1, Section 10 bans ex post facto state laws.

Many of the constitutional framers felt this was an important issue because Parliament was known to use the laws to retaliate against critics and opposing political groups. Alexander Hamilton called the laws 'instruments of tyranny' and Thomas Jefferson said the practice was 'against natural right.'

What Constitutes Ex Post Facto

To be constitutional, a law must pre-date a prosecution or punishment for violating that law. Let's take a closer look at what constitutes this type of constitutional violation.

As early as 1798, the Supreme Court set out what constituted an ex post facto violation. Ex post facto laws include:

  • Laws that make an action criminal and punish that act if the act was committed before the law was passed and the act was lawful when committed.
  • Laws that increase the severity of a crime over the crime's category at the time the crime was committed.
  • Laws that increase the punishment over the crime's punishment at the time the crime was committed.
  • Laws that decrease the amount of evidence or proof needed to convict a defendant from that required when the crime was committed.

Ex Post Facto and Civil Law

Ex post facto can also prohibit certain civil laws. Civil law governs conflicts between individuals, such as contract and property disputes. Most civil laws can be applied retroactively without violating the Constitution. However, if the primary purpose is to impose a penalty, then the law will be considered an ex post facto law. The Court decides by examining the legislative intent behind the law. In other words, the justices decipher what the lawmakers wished to accomplish by passing the law.

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