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 Rhode Island, 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 states, including Rhode Island. It allows a person held by the federal government to file a petition in court, typically against the prison warden, to demand a justification for their detention. The court must then evaluate the legality of the detention. If the government cannot show a lawful basis for holding the person, the court can order their release. This process is a civil action, not a criminal proceeding, and serves as a safeguard against arbitrary government action. Rhode Island state statutes and federal laws both recognize and protect this fundamental right, ensuring that individuals have recourse to challenge their detention in court.