Criminal Procedure

In addition to the amendments, the main body of the Constitution provides a number of provisions governing criminal procedure. Among these is a guarantee regarding writ of habeas corpus. In Latin, the phrase literally means "You should have the body," the first words of the original Habeas Corpus Act, adopted in England in 1679. Under the writ of habeas corpus, a defendant has a right to appear before a judge to determine whether he is being held illegally. During the Civil War, President Lincoln suspended the writ of habeas corpus in order to detain suspected Confederate agitators, using as his justification the provision in the Constitution which provides that "The privilege of the writ of habeas corpus shall not be suspended, unless when in cases of rebellion or invasion the public safety may require it." The Supreme Court ruled, in Ex parte Merriman (1861), that Lincoln had exceeded the powers granted the executive branch of government; however, Congress, in what remains a controversial act, authorized suspension of the writ for the duration of the war.

Other clauses in the Constitution which address criminal procedure include prohibitions against bills of attainder, a law declaring a person guilty without trial; and against ex post facto laws, or retroactive laws that attempt to punish someone for something that was not a crime when they did it. Finally, Article III, Section 2, provides for one of the foundational elements of the criminal justice system, trial by jury.