The Habeas Corpus petition claims the arrest, sentence, or trial violated constitutional law, making imprisonment unlawful. Habeas Corpus is technically defined as "may you have the body.A Writ of Habeas Corpus is a civil proceeding that is available in both State and Federal Court to challenge the legality of imprisonment. Petition for Writ of Habeas Corpus. The "Great Writ" of habeas corpus is a fundamental right in the Constitution that protects against unlawful and indefinite imprisonment. If you do not have a lawyer and are representing yourself in a case, use these simplified instructions to help you fill out the Military Affidavit form. Latin, meaning "you have the body. What is Habeas Corpus? LAW"). 3. Other ways of attacking your conviction include filing an appeal, or a state or federal writ of habeas corpus.