Frank Palko believed the Fifth Amendment's ban on double jeopardy applied to his case.

Frank Palko, who was the defendant in the famous Supreme Court case Palko v. Connecticut, 1937, indeed argued that the Fifth Amendment's protection against double jeopardy should apply to his case. Double jeopardy refers to the legal principle that no person should be tried twice for the same crime once they have been acquitted or convicted.

Initially, Frank Palko had been charged with first-degree murder, which carried the death penalty. He was convicted instead of second-degree murder and sentenced to life imprisonment. However, Connecticut appealed this decision, seeking a retrial. In the subsequent retrial, Palko was convicted of first-degree murder and sentenced to death.

Palko's case challenged the idea that the protections of the Fifth Amendment's double jeopardy clause were applicable to state legal proceedings as well as federal ones—this application of federal constitutional rights to state actions is known as "selective incorporation." At the time, the Supreme Court had not yet fully embraced the concept that the Bill of Rights protections were fully applicable to the states through the Fourteenth Amendment. Unfortunately for Palko, in a decision handed down on December 6, 1937, the Supreme Court decided 8-1 that the double jeopardy protection of the Fifth Amendment did not apply to state prosecutions (until later Court decisions began incorporating such rights via the Fourteenth Amendment), allowing the state of Connecticut to convict him of first-degree murder on retrial.