Palko (defendant) was indicted for first-degree murder and convicted of the lesser-included offense of second-degree murder. The law in the state of Connecticut (plaintiff) allowed the prosecution to appeal any errors of law in a criminal trial, and the prosecution appealed the judgment. The state court of appeals found errors of law with respect to the exclusion of evidence and flawed jury instructions. The state court of appeals ordered a new trial. Palko objected to a retrial on double-jeopardy grounds. Palko was convicted at the new trial and appealed the conviction through the state courts. Palko’s conviction was upheld by the state courts, and he petitioned the United States Supreme Court for review.