When countries seek to improve their judicial system, they usually tinker with the formal rules that govern the judiciary–tenure protections, salaries, and appointment arrangements. But there is a significant mismatch between the formal rules and actual judicial performance. For the past decade, then, scholars have explored informal institutions-social conventions and practices-that seem to shape judicial behavior. Informal norms can be as important as the formal institutional setup in determining judicial independence and competence. Yet, except for particular case studies, there is little comparative scholarship on the role of informal norms in the context of judicial selection. This leads to a straightforward question: How exactly does informality bleed into the selection of judges?

This Article provides a comparative study of the subterranean layer of informal norms that governs the selection of judges. Drawing on informal arrangements in Colombia, Mexico, Eastern Europe, and the United States, we explore how informality grows around judicial appointment processes and influences judicial performance. Our case study on Colombia builds on more than fifty interviews with government officials and judges. This allows us to offer a systematic understanding of how informal appointment mechanisms develop and exactly what role they play in different systems. We specifically identify three sites of informality that seem important in most countries: the process of pre-selection and vetting, the role of judicial guilds or corporatism, and the involvement of non-governmental organizations across the selection process. Normatively, we argue that differences in informal norms partially explain differences in de facto judicial independence and that countries need to plan for informality by seeding the ground for healthy norms to develop.