The justicar tradition is an old one, one that has its roots in Imperial history that predates the establishment of the magistrate system by the Emerald Champion and his associate, Soshi Saibankan. In Rokugan's earlier days, communication among the clans was less extensive and the lands between their holdings were wilder and more dangerous. This often resulted in criminals from one region fleeing to another and completely escaping prosecution. The lack of a strong Imperial network for the exchange of information only exacerbated this situation. However, Bushido demanded a solution to the problem, for a criminal fleeing the Lion lands might prey upon the Crane, bringing great dishonor to the Lion Clan (even though the Crane were hated enemies). The Dragon were thus not the first to establish a tradition of justicars, but they were the only ones to develop and maintain a fighting technique built on the tradition.
A justicar is essentially a magistrate trained in the art of dueling. The duty and purpose of a justicar is to travel in search of fugitives, sometimes hunting specific individuals and other times merely generally searching for anyone who may have escaped the justice of his clan. When he locates such an individual, the justicar challenges him to duel to the death. The death of the criminal retroactively proves his guilt and thus eliminates all problems. Of course, the possibility that the justicar may be killed (and thus the criminal exonerated) is somewhat of a problem but even in this case the clan is freed from any dishonor since the victor was clearly not a criminal before he arrived at his new home.
Since the Kitsuki family's founding, their strong emphasis on justice has led them to embrace the justicar tradition and they have developed a technique to support it. Kitsuki justicars typically hold a post as a Dragon Clan magistrate, and the clan often goes to considerable effort to get them appointed as Emerald Magistrates as well, though success in this depends on the relationship between the Kitsuki family and the Emerald Champion at the time.