The writ of habeas corpus is an important judicial right affecting court proceedings in that it empowers a detainee to petition the court and have the State justify its decision for detention, according to Cornell University Law School. The right has been expanded to allow state prisoners to petition federal judges.
The phrase "habeas corpus" means "that you have the body," a call from a judge to an authority to prove the legality of holding a detainee, reports Cornell Law School. As conceived, it was meant to protect an individual from being held in custody without being charged with an offense. Although such protection is still very much in place, in the contemporary American judicial system, the writ has been most often employed by state prisoners who have been convicted and petition federal courts about wrongful conviction. The writ is also more commonly used in immigration cases and by military prisoners and detainees. According to the Constitution, only Congress has the power to suspend the privileges of the writ in cases in which "the public safety may require it."
The expansion of the writ during the middle years of the 20th century has regressed in the two decades leading up to 2015 with the ascendancy of a more conservative federal bench, according to the American Prospect. During those decades, Republicans in Congress have also led the way to place limitations on the writ as anti-terrorism measures.