Whether Connecticut's resolution ordering a new probate hearing was an ex post facto law prohibited by Article I, Section 10 of the Federal Constitution.
Holding
No. The Ex Post Facto Clause applies only to retrospective criminal or penal laws, not to retrospective civil legislation affecting property rights or judicial proceedings.
Reasoning
Justice Chase treated the phrase "ex post facto law" as a legal term of art rather than as a literal ban on every law enacted after an event. In its constitutional sense, the prohibition protects individuals from retrospective legislative punishment for past conduct.
He identified four prohibited categories: a law making previously innocent conduct criminal; a law aggravating an existing crime; a law increasing the punishment for a past offense; and a law changing evidentiary rules to permit conviction on less or different proof than the law previously required.
The Connecticut resolution did not punish anyone for prior conduct, alter the definition of a crime, increase a punishment, or ease the proof needed for a criminal conviction. It instead reopened a civil probate dispute and ultimately affected which claimants would receive property.
The Court distinguished ex post facto laws from retrospective laws. Every ex post facto law is retrospective, but not every retrospective law is ex post facto. Retrospective civil measures may be unfair or oppressive, but they are not invalid under this particular constitutional prohibition.