Right Against Ex Post Facto Law and Bill of Attainder (Sec. 22, Art. III)

An ex post facto law is a law which operates retroactively and makes an act done before its passage, innocent when done, criminal, or makes the crime greater than when it was committed, or inflicts a greater punishment than what the law provided to the crime when it was committed, or alters the legal rules of evidence and receives less testimony than what the law required at the time of the commission of the offense in order to convict the offender.

In general, criminal laws cannot be given retroactive effect. But if it is favorable to the accused, it should be should be given retroactive effect.

A bill of attainder is a legislative act which inflicts punishment without a judicial trial.