The term mutual trust has become a household term in the EU criminal justice vocabulary and is regarded to be a prerequisite for a successful application of the principle of mutual recognition. Regardless of its widespread use, it is often used in the vernacular, as if clear in itself. But as mutual trust has become one of the core objectives of the EU's criminal justice policy, and legislation is adopted to build trust, more specificity is required. This article attempts to unpick the notion of trust into its various elements. The argument is put forward that next to the principle's legal and political components, it also consists of more 'social' elements, as trust is a social construct after all. An assessment of the concept of trust developed in the social sciences reveals these additional elements and puts forward the idea of trust as a hybrid notion.