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. The writ of habeas corpus primarily acts as a writ of inquiry, issued to test the reasons or grounds for restraint and detention.The "Great Writ" of habeas corpus is a fundamental right in the Constitution that protects against unlawful and indefinite imprisonment. Find definitions for specific words, phrases, and terminology used in the Massachusetts Court System. (8)(9) Family relations matters defined. The forms listed below are used in civil and criminal cases in the Superior Court. They are for lawyers and for people who do not have lawyers. For example, when a court issues a writ of habeas corpus, it demands that the person who is detaining you release you from custody. Entertain an application for a writ of habeas corpus in behalf of a person in custody pursuant to the judgment of a State court only on the ground that he. McCARTHY, District Judge.