Palko v. Connecticut

Palko (defendant) was convicted of second-degree murder after being indicted for first-degree murder, and Connecticut's law allowing prosecutorial appeal of trial errors let the state appeal evidentiary and jury-instruction errors, resulting in a new trial where Palko was convicted again; he challenged the retrial on double-jeopardy grounds, arguing the Fifth Amendment's protection should apply to the states through the Fourteenth Amendment.