The Decision making trial and evaluation laboratory (DEMATEL) method is a powerful method for capturing the causal relationship between criteria and has been successfully applied to crisp situations. However, in many real life cases, the decision data of human judgments with preferences are often vague so that the traditional ways of using crisp values are inadequate. In this paper, the directed influential degrees between pair wise criteria are expressed in trapezoidal fuzzy numbers is used in DEMATEL method to study on youth violence. Violence is a problem which affects our day today life in a severe way. Even though human beings have been struggling to create civilized societies for many years, they have not able to get free from the influence of violence and aggression yet. Aggressiveness among youth is considered to be a global public health problem in many parts of the world. The existence of violence around a person might provoke him to behave in a more violent way. So in this paper we analyze what makes the youth to be aggressive behavior and involving in violence and its effect