In criminal procedure, the cornerstone of the proceeding governing the establishment of crucial facts is the opportunity of the parties to present their arguments on the criminal matter at issue and to challenge the opponent’s arguments, which is the focal point of the adversity principle in criminal procedure. A criminal proceeding, which is legally regulated as a dispute involving parties with an equal procedural standing, is an optimal institutional setting for accomplishing the proclaimed purpose of the criminal procedure. It gives rise to the importance of the principle of adversity, which is not explicitly stipulated in the Criminal Procedure Code but which is indisputably derived from the position of the adversaries in criminal procedure. Although the adversity principle is primarily put into effect in the course of the main hearing (trial proceedings), the elements of this principle may also be present in other stages of criminal procedure. The basic condition for implementing the adversity principle is the normative framework where the criminal procedure is regulated as an adversarial procedure. In the contemporary criminal procedure, the monofunctionality principle is one of the basic features of both adversarial and continental criminal procedure which provides for exercising the adversity principle.