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 Colorado, as in all states, habeas corpus is a fundamental legal procedure protected by both the United States Constitution and state law. It serves as a safeguard against unlawful detention by the federal government, ensuring that no person can be held indefinitely without just cause. Under Article I, Section 9, Clause 2 of the U.S. Constitution, the right to petition for a writ of habeas corpus is a protection against the suspension of this critical check on governmental power. When a person in federal custody believes they are being held unlawfully, they can file a habeas corpus petition. This action requires the government to present a valid reason for the individual's detention to a neutral federal judge. In Colorado, federal courts would handle these petitions, and the process is treated as a civil matter, with the government agent responsible for the detainee's custody, typically the prison warden, named as the respondent. The writ of habeas corpus is a cornerstone of American legal rights, reflecting the Founders' intent to prevent government overreach and protect individual freedoms.