In this paper, I discuss the legislation of criminal laws in the early Joseon dynasty through a case study. It was the homicide case between two brothers in 1478 (the 9th year of King Seongjongs reign). Despite the simplicity of the case, almost 40 higher officials in the royal court participated in the discussion of the case. The reason why the higher officials took the case seriously was that the older brother was a son by a concubine and the younger was a son by the legal wife. There was a deep and rigorous distinction between sons by the legal wife and sons by concubines in the Joseon dynasty. The higher officials thought that the social status order by birth legitimacy was not reflected adequately in The Great Ming Code, the basic criminal code in the Joseon dynasty. They reinterpreted the case from various perspectives in order to establish the firm social status order between sons by the legal wife and sons by concubines. Not only the number of higher officials participating in the discussion, but also the different legal opinions presented in the royal presence exemplify the process and the reasoning of making new criminal laws in the early Joseon dynasty
