Habeas corpus means produce the body: the state must bring a prisoner into open court and justify the detention to a judge. It is often credited to the Magna Carta of 1215, but that charter offered a principle, not a procedure. The working machinery traces to the Assize of Clarendon in 1166 under Henry II, and similar tools appeared independently across medieval Europe, from Aragon’s manifestation of persons in 1325 to a Polish royal privilege of 1430. Wherever central power grew, people found they needed a piece of paper that could force a ruler’s agents into the light.

This episode follows the writ from those origins to the Habeas Corpus Act of 1679, passed by Whig leaders who feared Charles II would lock them in the Tower of London, and then to its recurring weakness: governments suspend it when they feel threatened. Lincoln, Grant, and Franklin Roosevelt did so, as did Canada and the Philippines. The story ends with two twentieth century attempts to place the protection beyond a government’s reach, one through the United Nations and one written into the constitution of India.

• Biscay’s charter of 1526 required that a person be summoned to the oak of Guernica and given 30 days to answer before any arrest.
• Charles II was so angry at the 1679 act that he dissolved the body that passed it, remembered since as the Habeas Corpus Parliament.
• Grant suspended the writ during Reconstruction because local judges sympathetic to the Ku Klux Klan were using it to free arrested Klansmen.
• In 1952 lawyer Luis Kutner petitioned for a United Nations writ on behalf of William Oatis, an American journalist jailed in Czechoslovakia, who was released a year later.
• B.R. Ambedkar wrote the power to issue the writ into Articles 32 and 226 of the Indian Constitution, a safeguard tested in the Rajan case during the Emergency.