The Collaborative International Dictionary
Ex post facto \Ex" post` fac"to\, or ||Ex postfacto \Ex" post`fac"to\ ([e^]ks" p[=o]st" f[a^]k"t[-o]). [L., from what is done afterwards.] (Law) From or by an after act, or thing done afterward; in consequence of a subsequent act; retrospective.
Ex post facto law, a law which operates by after enactment.
The phrase is popularly applied to any law, civil or
criminal, which is enacted with a retrospective effect,
and with intention to produce that effect; but in its true
application, as employed in American law, it relates only
to crimes, and signifies a law which retroacts, by way of
criminal punishment, upon that which was not a crime
before its passage, or which raises the grade of an
offense, or renders an act punishable in a more severe
manner that it was when committed. Ex post facto laws are
held to be contrary to the fundamental principles of a
free government, and the States are prohibited from
passing such laws by the Constitution of the United
Douglas Harper's Etymology Dictionary
a. 1 retroactive 2 (context legal English) formulate or enacted after some event, and then retroactively applied to it.
"Ex Post Facto" is the eighth episode of Star Trek: Voyager. The episode's title is Latin for "from a thing done afterward", and refers to the concept of retroactive law.
Usage examples of "ex post facto".
Subsection Forty-Two specifically provided for wartime trials of individuals for alleged violation of local laws (in this case the Peeps' own UCC, since Hell had been sovereign territory of the People's Republic of Haven at the time) predating their capture, but prohibited ex post facto trials under the municipal law of whoever captured them.
Especially the construction sketch, but the ex post facto crayon drawing as well, suggested a dancer tightly clad in the late reflected splendor of a uniform worn by the musketeers of the Prince of Anhalt-Dessau Infantry Regiment at the battle of Liegnitz.
The technical question was whether Congress had the right to pass ex post facto legislation affecting a candidate already elected.
I immediately noticed the similarity between the transcript of Wyoss's bizarre ramblings and the few recordings and ex post facto accounts of the dead murderers.