In the last decades, in absentia proceedings (i.e. criminal proceedings conducted in the defendant's absence) have fuelled much controversy among scholars for their alleged incompatibility with International Human Rights Law standards. However, the phenomenon of absent defendants in international criminal proceedings (especially when fugitives) is a serious threat to the achievement of justice at the international level, and it prompts pressing questions regarding the fight of impunity and the effective prosecution of international crimes. This thesis seeks to shed light on in absentia proceedings, providing an innovative analysis of their theory and practice. It examines these procedures in the context of International Criminal Justice and addresses the following research question: what are the limits and prospects of the use of in absentia proceedings for the prosecution of international crimes in International Criminal Justice? To answer this question, the author conducts a three-part study of international criminal proceedings in absentia that focuses on their foundations, operation, and future perspectives. This thesis combines an examination of the existing literature on the topic (including relevant case law and norms) with a critical analysis of the opinions of legal practitioners who have been and are involved in in absentia proceedings at the Special Tribunal for Lebanon and the International Criminal Court. Through this approach, the author seeks to provide an innovative, comprehensive study of in absentia proceedings that overcomes the traditional, limited scholarship's analysis of the topic. The author posits that in absentia proceedings can play a significant role in International Criminal Justice for the prosecution of international crimes when the defendants are absent. However, they are limited by a set of theoretical (e.g. objectives of International Criminal Justice; International Human Rights Law standards) and practice-based elements (e.g. practice of international criminal tribunals; exigencies of the parties of international criminal cases). Ultimately, the author proposes a new understanding of these procedures as useful, legally possible, but exceptional.