Ex parte Yarbrough was a United States Supreme Court case that dealt with the issue of whether a writ of habeas corpus should be granted to a prisoner who had been convicted of a crime in a state court. The petitioner, Yarbrough, had been convicted of murder in a state court and was sentenced to death. He then filed a petition for a writ of habeas corpus in the Supreme Court, arguing that his conviction was unconstitutional because the state court had failed to provide him with a fair trial. The Supreme Court ultimately denied Yarbrough's petition, ruling that the state court had provided him with a fair trial and that the writ of habeas corpus was not necessary. The Court reasoned that the state court had followed the proper procedures and that Yarbrough had been given a fair trial. Furthermore, the Court noted that the writ of habeas corpus was not intended to be used as a substitute for a trial, but rather as a means of ensuring that a prisoner's constitutional rights were not violated. In conclusion, the Supreme Court denied Yarbrough's petition for a writ of habeas corpus, ruling that the state court had provided him with a fair trial and that the writ of habeas corpus was not necessary. The Court's decision established that the writ of habeas corpus should not be used as a substitute for a trial, but rather as a means of ensuring that a prisoner's constitutional rights were not violated.

In Ex Parte Yarbrough, the Supreme Court was asked to decide whether a federal court had jurisdiction over an indictment for conspiracy against two individuals who were charged with conspiring to deprive African-American citizens of their right to vote. The majority opinion held that the federal courts did have jurisdiction in this case and could proceed with prosecution. Justice Field dissented from this decision on the basis that Congress had not given any authority or power to punish conspiracies against voting rights under existing laws at the time of the alleged offense. He argued that it would be unconstitutional for Congress to pass such a law after an offense has been committed, as doing so would violate due process by punishing someone retroactively without giving them prior notice of what they are being accused of doing. Furthermore, he argued that if Congress wanted these types of offenses punishable by law then it should have done so before any crime was committed rather than attempting to do so afterwards when it is too late for those involved in criminal activity at issue here.