Needles in a haystack: using network analysis to identify cases that are cited for general principles of law by the European Court of Human Rights

In this chapter, we propose two different methods to identify what we call polymorph principles in the practice of the European Court of Human Rights, i.e. principles of law that are not directly related to the interpretation of one or few articles in the convention, but are applicable to a case independent of its substantial content. Examples of these principles could be interest rates when states pay reparations, the quality of evidence or the relation between the ECtHR and the contracting states. Since these transverse precedents are not easily identifiable in the ECtHR’s own database and since they are only occasionally taken under direct treatment in textbooks, we propose two methods to extract them from the more than 17.000 judgments that comprise the practice of the ECtHR. We use the citations between judgments to identify patterns where a precedent is cited by many different types of cases, indicating that the precedent is relevant no matter what article constitute the core of the case. We conclude that the two different methods, both building directly on earlier research in automatic identification of case content based on citations to other cases and convention articles, yield satisfying results and provides another angle of entrance to the practice of the ECtHR, especially when combined to remove the largest possible amount of false positives.