A writ of habeas corpus is a judicial mandate to a prison official, usually the warden, ordering that an inmate be brought to the court. A Writ of Habeas Corpus is a civil proceeding that is available in both State and Federal Court to challenge the legality of imprisonment.The writ of habeas corpus primarily acts as a writ of inquiry, issued to test the reasons or grounds for restraint and detention. Habeas Corpus, in the Federal Court, is a petition that claims that you are being detained against your US constitutional rights. The writ of habeas corpus, also known as the Great Writ, is a U.S. legal process that determines whether an offender's imprisonment is valid. To get a writ of habeas corpus, you must file a petition for a civil (not criminal) proceeding in either state or federal court. A writ of habeas corpus is used to bring a prisoner or other detainee (e.g. The "Great Writ" of habeas corpus is a fundamental right in the Constitution that protects against unlawful and indefinite imprisonment. A Writ of Habeas Corpus. The basis for such an application is DRL §70.