Habeas corpus—also known as the Great Writ—is the legal procedure that prevents the federal government from arresting and holding (in prison) a person indefinitely without showing cause for detaining the person. This Latin term is pronounced "Hay-bee-us Corp-us."

A person detained by the federal government may challenge their detention by filing a habeas corpus petition—which then requires the government to explain to a neutral judge the justification for detaining the person. A habeas petition is prosecuted or litigated as a civil (noncriminal) matter against the government agent (usually the prison warden) who holds the defendant in custody.

The Founders of the United States who wrote the U.S. Constitution believed so strongly in this protection against government overreach they included it in the first article of the Constitution (Article I, Section 9, Clause 2).

In South Dakota, as in all states, the principle of habeas corpus is a critical component of the legal system, providing a means to challenge unlawful detention. Habeas corpus, enshrined in Article I, Section 9, Clause 2 of the U.S. Constitution, is a federal right that applies to all individuals within the United States, including those in South Dakota. If a person is detained by the federal government, they can file a habeas corpus petition in a federal court. This petition obligates the government to present a valid legal basis for the individual's detention to a neutral judge. If the government cannot justify the detention, the judge can order the release of the detainee. This process is a civil action against the person (typically a prison warden) responsible for the detainee's custody. It is important to note that while habeas corpus is a federal right, state prisoners in South Dakota can also seek relief through state habeas corpus procedures under state law, which are generally consistent with federal habeas corpus principles but may have specific state statutes and rules governing their application.