Which legal principle protects individuals from being held in custody without a court hearing?

The principle that protects individuals from being held in custody without a court hearing is known as habeas corpus. This legal doctrine requires that a person who has been detained or imprisoned be brought before a court, so that the court can determine whether the detention is lawful. The purpose of habeas corpus is to prevent unlawful detention and ensure that individuals' rights are respected within the legal system.

Habeas corpus acts as a safeguard against arbitrary imprisonment by allowing individuals to challenge the legality of their detention. If someone is imprisoned, they (or someone on their behalf) can petition for a writ of habeas corpus, prompting a court to review the circumstances of their detention. This principle is deeply rooted in the common law tradition and recognized in many legal systems as a fundamental civil right.

In contrast, due process refers broadly to the legal requirement that the state must respect all legal rights owed to a person, encompassing fair procedures and trials but not specifically addressing the immediate right to be informed of the reasons for detention. Ex post facto laws are those that make an action illegal retroactively, and probable cause relates to the legal standard required for law enforcement to conduct searches and make arrests, but neither directly addresses unlawful detention like habeas corpus does.