I keep hearing Habeas Corpus in the news and I just had to look it up. This is what I found:
Lat. “you have the body” Prisoners often seek release by filing a petition for a writ of habeas corpus. A writ of habeas corpus is a judicial mandate to a prison official ordering that an inmate be brought to the court so it can be determined whether or not that person is imprisoned lawfully and whether or not he should be released from custody. A habeas corpus petition is a petition filed with a court by a person who objects to his own or another’s detention or imprisonment. The petition must show that the court ordering the detention or imprisonment made a legal or factual error. Habeas corpus petitions are usually filed by persons serving prison sentences.
inserted from http://www.lectlaw.com/def/h001.htm