It tests the legality of a detention or a restraint and the goal is to use it really almost i guess it's an emergency basis. A Federal Writ of Habeas Corpus is a procedure where federal courts with national power can review the legality of an individual's incarceration.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 is used to bring a prisoner or other detainee (e.g. Habeas corpus is used to challenge the legality of the detention or restraint of a person and to obtain the person's prompt release. 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. Writ of Habeas Corpus a civil case number and assign it to the judge assigned to the pending writ with the lowest case number. 'Habeas Corpus' literally means "to have a body of". This writ is used to release a person who has been unlawfully detained or imprisoned. Habeas corpus literally means, "you have the body.