The aim of this study is to analyze the use of the terms asebeia and hybris in the forensic discourses contained at the corpus Demosthenicum. Both of these concepts play an important role in the discourse to describe negatively the character of the opponent and to assign a greater guilt to the offense committed. The efficiency of these terms in attracting the sympathy of the judges in the discourses is proven by their recurrence about various situations, such as homicide, assault, misuse of citizenship, political rivalries and family quarrels. This study was divided into three parts. The first is devoted to a discussion of the methodological issues, the second deals with the notions of asebeia and hybris in the Archaic and Classical period and, finally, the third is about the use of such notions in the world of the speakers, mostly in Demosthenes. The third part is divided into seven chapters, each of them is dedicated to a specific use of such notions. Demosthenes has chosen carefully the use of the notions of asebeia and hybris to compose the negative ethos of the opponent. He has done that by enriching the prosecution with factors that are not necessarily connected to the main legal action, but are reprehensible in the eyes of citizens. Thus, both of these notions are widely used in cases where the tradition of the city is in danger.