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).

Habeas corpus, often referred to as the Great Writ, is a fundamental legal procedure enshrined in the U.S. Constitution that protects individuals from being detained indefinitely without just cause. In West Virginia, as in all states, a person held by the federal government can file a habeas corpus petition to challenge their detention. Upon filing, the government must present a valid reason for the individual's imprisonment to a neutral judge. This process is considered a civil action against the custodian of the detainee, typically the prison warden. The right to habeas corpus is so central to American legal principles that it was explicitly included in Article I, Section 9, Clause 2 of the U.S. Constitution. While federal law governs the process for federal detainees, state habeas corpus procedures are also available for those held under state authority, and these are governed by state statutes that align with federal principles to ensure protection against unlawful detention.