No official executions were carried out in Japan for over 300years during the Heian period from the Kōnin era to the time of the Hōgen Rebellion. This fact has long been known, and has been taken up in many documents thus far. On the premise that this was not an abolition of the death penalty but a suspension, after examining the period and conditions pertaining to this suspension, this paper attempts to discuss the background and causes leading to such a phenomenon, and to explain the historical significance of this suspension in capital punishments. Various points have been made thus far regarding the background and causes of this suspension in capital punishments, all of which are understood to be factors. Among them a fear of vengeful spirits in particular has been most emphasized, and the author formerly subscribed to that idea. However, because there are cases in which execution was condoned even for serious crimes clearly committed by commoners not related to unreasonable deaths, a fear of vengeful spirits is not an adequate explanation. Also, such reasons were hardly discussed when resuming capital punishment, and there is even the opinion that in later aristocratic society executions were fundamentally avoided. This paper takes as its hypothesis the idea that executions were later carried out in aristocratic society and based on an analysis of the Go-Shirakawa Tennō Senmyō-an, defilement was seen as the greatest issue, and through the medium of defilement, examined its relationship with the situation pertaining to the Emperor and his court, and changes in imperial authority. The Go-Shirakawa Tennō Senmyō-an promulgated after the Hōgen Rebellion is a historical source that is often cited. This paper in particular focuses on the passage on the delay, due to the defilement of death, of the report made before the gods of the details of the rebellion and how it was subsequently handled. Defilement resulting by execution can be understood as a major issue. Defilement was systematized after the mid-ninth century, and was parallel to the process of purifying the emperor as high priest. The sanctioning of executions by the emperor gradually dropped off to avert the defilement of death, and the carrying out of executions was avoided to prevent the effects of such defilement on the court and palace. In this way, after a long hiatus capital punishment was resumed following the strife of the Hōgen Rebellion. This was not simply about the arising of the warrior families, but was also a major transformation in aristocratic society involving the court and emperor. At the point of the complete purification of the emperor as high priest, a new form of government was established, the cloistered government, and the retired emperor as a secular ruler exercised authority as the actual ruler. Moreover, as the concept of defilement became secularized, rarefied, and diffused, the earlier desire to avoid executions weakened. As a result, the emperor was able to preserve his purity, and the way was opened for the retired emperor to become involved in legal punishments and to sanction executions. The death penalty in Japan was suspended after the Kusuko Incident, and was resumed after the Hōgen Rebellion. Both were confrontations between a retired emperor and an emperor, and developed through a splitting of imperial authority. A suspension and resumption of the death penalty, it arose within the process of shifts in imperial authority, and was a unique phenomena.