In legal science, it is generally known that applicable legal rules are found in legal sources, a vaguely defined circle of authoritative sources of information, and that case law is one of these. However, no clear answer as to how and to what extent case law functions as a source of law in the Swedish legal system is available, and can hardly be achieved through traditional legal science methods alone. By analyzing an extensive number of decisions by Swedish courts over a long period of time, the project aims to empirically establish the importance of case law as a source of law. Traditional legal science methods are supplemented with statistics and network analysis to answer questions such as which decisions become precedents, in which areas of law is case law particularly important as a source of law, how does the case law of different instances affect each other and how has this changed over time.