This monograph explores the complex area of pre-trial criminal proceedings, examining the intricate legal aspects that arise during this crucial phase of the legal process. Based on the foundations of current criminal procedural law, judicial practice, and the most recent academic literature, this work dives deep into the challenges of pre-trial proceedings, with a particular focus on the institutions of preliminary investigation, initiation of criminal proceedings, refusal to initiate criminal proceedings, and preliminary inquiries. The monograph thoroughly examines the theoretical foundations and legal nature of the relationships that arise at the start of the criminal justice process. Furthermore, it explores a comparative analysis of international experiences in criminal prosecutions, providing a comprehensive view of the complexities of pre-trial proceedings. Through a thorough examination of criminal procedural regulations, law enforcement practices, and best international practices in regulating the pre-trial stage, this study proposes innovative solutions to improve both the efficiency of legal frameworks and the effectiveness of law enforcement agencies. This work is particularly relevant to members of legislatures, members of judicial bodies, including prosecutors, judges, and legal professionals, as well as academics, educators in the field of criminal law, researchers, and students of law schools and faculties of law.