What is habeas corpus, and what does it do?

Habeas corpus is a legal procedure that invokes a court's authority to decide whether a detention or imprisonment is lawful. The Latin phrase is usually translated as "you have the body" or "produce the body." A court issues the writ, an order requiring the authorities holding a person to bring that person before the judge and justify the confinement. If the government cannot show a lawful basis, the person must be freed. [1] [2] [3]

The Brennan Center dates the writ, sometimes called the Great Writ, to the Magna Carta of 1215, and describes it as protection against a king making subjects vanish into secret dungeons without cause or due process. The Library of Congress similarly says King John's Magna Carta guaranteed free men immunity from illegal imprisonment, a guarantee traditionally invoked through the writ of habeas corpus. In Anglo-American law, people deprived of liberty can challenge the legality of their arrest or detention through a judicial inquiry. [2] [4]

The US Constitution protects it directly. It says the privilege of the writ shall not be suspended, except in cases of rebellion or invasion when public safety may require it. [2]

The writ tests the legality of a detention, not guilt or innocence. According to Cornell's Legal Information Institute, the reviewing court examines whether the authorities had the power to detain the person, not whether their conclusion was correct. A habeas petition proceeds as a civil action against the official holding the person in custody. The writ can also be used to bring a person before a court to testify or to be prosecuted. [5] [1]

Today habeas is mainly a post-conviction remedy. Federal judges receive petitions from state prisoners who say their prosecutions violated federally protected rights, and federal prisoners may petition too. Typical claims are that a lawyer failed to represent the person adequately or that prosecutors illegally withheld key evidence. Habeas is also available to citizens and noncitizens challenging immigration detention, for example detention without legal basis or for an unduly long period, though Congress has limited its use against deportation orders themselves. [2] [5]

It is hard to win. The Brennan Center reports about 12,000 filings a year, with data that is sparse but suggests success a little over 10 percent in capital cases and under 1 percent in others. A win may only mean a new trial. A 1996 law bars federal courts from overturning a state conviction unless state court decisions significantly conflict with Supreme Court precedent. A Congressional Research Service overview describes the premise as giving prisoners "one bite of the apple," with strict time limits. [2] [6]