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 New Mexico, as in all states, the principle of habeas corpus is a critical safeguard against unlawful detention. It is enshrined in the U.S. Constitution and applies to federal detentions. A person in New Mexico who is detained by the federal government can file a habeas corpus petition to challenge the legality of their detention. Upon filing, the government must present a valid legal reason for the individual's imprisonment to a neutral judge. This process ensures that no one is held indefinitely without just cause, reflecting the importance the Founding Fathers placed on this right to protect individuals from government overreach. While habeas corpus is primarily a federal concept, state laws also provide similar protections against unlawful state detentions. In New Mexico, state statutes outline the procedure for filing a habeas corpus petition in state courts, ensuring that individuals detained under state law also have a mechanism to contest their imprisonment.