Law: the Great Writs-Habeas Corpus

Much of American law owes its roots to England, whether its the Anglo-Saxon jury, or the common law and writs of Plantagenet kings such as Henry II, Edward I and Edward III, the procedures that we think of as due process in criminal and civil matters have an origin of several hundred years.

In the Medieval era, the king was both law giver, judge and law enforcement.  Wherever the King was, courts or assizes would be held.  Judges, or sometimes the King, would hear cases, settle disputes and dispense justice, sometimes by ordering an offender hanged, fined or dispossessed of lands.  This system could be quite chaotic in practice, as the King couldn't be everywhere at once and couldn't possibly hear every case.  Henry established a system of royal assizes or courts staffed by judges and clerks would could hear cases and decide punishments in his absence.  And, where there are courts and clerks, there has to be procedure.  One of the earliest forms of procedure were writs, written authorizations for certain acts to be done. 

One of these writs, often called the Great Writ, was Habeas Corpus, literally Latin for "have the body", i.e., have a person brought before a judge to determine if the person should be placed on trial.  Potential defendants wouldn't be allowed to just languish in jail without benefit of trial, or summarily executed or dispossessed on whim, but could be brought before a judge to determine whether they needed to be held for trial or released.  Though some people believe this writ is a result of the Magna Carta of 1214, in fact it originated much earlier, at the Assizes of Clarendon based on an act drawn up by Henry II in 1166.  Henry wanted to phase out trial by ordeal or combat and replace these with trial by evidence.  One of the courts provided for in the act took place at Clarendon Palace, hence the name.  In 1214, Magna Carta affirmed that no free man would be imprisoned or dispossessed or otherwise condemned without judgement of his peers, i.e., a trial.  During the reign of Edward I, the powers of the writs were expanded and over time various types of habeas corpus writs developed, including writs for extradition, remand to another court, etc.