In the medieval England and Scotland, a justiciar was an important legal and political figure. The Latin justiciarius means simply judge.

England

In the history of England, the term justiciar originally referred to any officer of the king's court (curia regis), or, indeed, anyone who possessed a law court of their own or was qualified to act as a judge the shire-courts.

The chief justiciar (latterly known simply as the justiciar) was a rough equivalent to that of the modern Prime Minister: the monarch's chief minister.

In each shire, the sheriff was the king's representative in all matters. The only appeal from decisions of the sheriff, or his courts, was to the king. However, the king was often overseas (and, in the early Norman period, did not understand the language of his subjects) so a justiciar, regent or lieutenant was appointed to represent the king in the kingdom, as the sheriff did in the shire.

As early Norman kings were often overseas, and the justiciar was invariably a great noble or churchman, the office of justiciar became very powerful and important; indeed, important and powerful enough to be a threat to the king. The last great justiciar, Hubert de Burgh, was removed from office in 1231, and the Lord Chancellor soon took the position formerly occupied by the justiciar as second to the king in dignity, as well as in power and influence.

The office of chief justiciar is thought to have existed from the reign of William II, when Ranull Flambard was justiciar, until, under Edward I, the office of justiciar was replaced by separate heads for the three branches into which the king's court was divided: Justices of the Court of Common Pleas, Justices of the Court of King's Bench and Barons of the Court of Exchequer.

Scotland

In Scotland, the title of 'justiciar' was historically borne by two high officials, one having his jurisdiction to the north, the other to the south, of the River Forth. They were the king's lieutenants for judicial and administrative purposes and were established in the 12th century.

Other jurisdictions

The title justiciar was given by Henry II to the seneschal of Normandy.

In the 12th century, a magister justitiarius appeared in the Norman kingdom of Sicily, presiding over the royal court (magna curia). It is thought that this title and office were borrowed from England.