Openness and transparency have become defining goals for policy initiatives worldwide. Transparent and open political processes increase legitimacy by holding public institutions accountable and promote public trust by allowing public scrutiny. In the context of judiciaries, this discussion is informed by the open justice principle. This principle requires that the process of justice be visible, which in turn promotes trust in legal systems because citizens can see how justice works. However, scholars lack both a clear definition and approaches to measuring open justice in the courts. This chapter aims to establish open justice as a new avenue for comparative research in judicial politics by proposing a conceptualization and a measurement of the principle. Using data on trust in the legal system in 27 European countries, the chapter contributes to the literature by presenting the first empirical evidence for the assumption that open justice increases public trust.