What legal process allows a person in custody to seek relief from unlawful imprisonment?

The correct answer is habeas corpus, which is a legal process that enables individuals in custody to challenge the legality of their imprisonment. This principle is enshrined in law and serves as a crucial protection against unlawful detention.

When a person asserts a habeas corpus claim, they are essentially asking the court to examine whether they are being held in violation of their legal rights. This process ensures that the government cannot detain individuals without just cause and provides a mechanism for individuals to contest their detention.

In contrast, a subpoena is a legal document that orders a person to testify or produce evidence, but it does not relate to challenging detention. Due process appeal refers to the broader concept of ensuring a fair legal process, but it is not specifically a mechanism for addressing unlawful imprisonment. An injunction is a type of court order that requires a person to do or refrain from doing a specific action, which also does not pertain directly to challenging one's custody.

Thus, habeas corpus stands out as the established legal remedy for seeking relief from unlawful imprisonment.