Definition of Ex Post Facto Law
A law passed after the occurrence of a fact or commission of an act, which retrospectively changes the legal consequences or relations of such fact or deed. By Art. I, § 10 of U.S.Const., the states are forbidden to pass “any ex post facto law.” Most all state constitutions contain similar prohibitions against ex post facto laws.
An "ex post facto law” is defined as a law which provides for the infliction of punishment upon a person for an act done which, when it was committed, was innocent; a law which aggravates a crime or makes it greater than when it was committed; a law that changes the punishment or inflicts a greater punishment than the law annexed to the crime when it was committed; a law that changes the rules of evidence and receives less or different testimony than was required at the time of the commission of the offense in order to convict the offender; a law which, assuming to regulate civil rights and remedies only, in effect imposes a penalty or the deprivation of a right which, when done, was lawful; a law which deprives persons accused of crime of some lawful protection to which they have become entitled, such as the protection of a former conviction or acquittal, or of the proclamation of amnesty; every law which, in relation to the offense or its consequences, alters the situation of a person to his disadvantage. Wilensky v. Fields, Fla., 267 So.2d 1, 5.
That's the definition of Ex Post Facto Law in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.
