EXPOS'ITORY, adjective Serving to explain; tending to illustrate.
Ex post facto. [Latin] In law, done after another thing. An estate granted may be made good by matter ex post facto, which was not good at first.
An ex post facto law, in criminal cases, consists in declaring an act penal or criminal, which was innocent when done; or in raising the grade of an offense, making it greater than it was when committed, or increasing the punishment after the commission of the offense; or in altering the rules of evidence, so as to allow different or less evidence to convict the offender, than was required when the offense was committed.
An ex post facto law is one that renders an act punishable in a manner in which it was not punishable at the time it was committed.
This definition is distinguished for its comprehensive brevity and precision.
In a free government, no person can be subjected to punishment by an ex post facto law.