Legal relevance refers to a characterization process that consists of making a factual situation correspond to a formal legal definition. Professionals’ work is very largely made of the formalization of categories that are enunciated in the narratives of facts elaborated by the parties to a trial. In other words, writing up a trial responds to a formal requirement – the ascription of legal consequence to an action – that does not necessarily corresponds to the protagonists’ orientation. In this chapter, we seek to describe the process of legal abstraction in which professionals are engaged, and the implied transformation of factual statements as formulated by lay participants in a judicial interaction.