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 Virginia, as in all states, habeas corpus is a fundamental legal procedure that protects individuals from being detained indefinitely without just cause. This right is enshrined in the U.S. Constitution and applies to both federal and state detentions. When a person is detained by the federal government in Virginia, they have the right to file a habeas corpus petition. This petition compels the government to present a valid reason for the individual's detention to a neutral judge. The process is civil in nature and is typically directed against the government official responsible for the detainee's custody, often the prison warden. The writ of habeas corpus serves as a check on governmental power and is a critical component of the United States' legal system, reflecting the Founding Fathers' commitment to protecting individual liberties against government overreach.