FOREWORD “If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.” (Rene Descartes) What is doubt and what kind of feeling is doubt? Should a judge being an independent arbiter not be doubtful for the most time of the trial? Nonetheless, is the judge not required to decide at the end? How can a judge decide if in doubt, and can a judge remain in doubt despite all? The criminal procedure principle in dubio pro reo-when in doubt in favour of the defendant- and the standard that the guilt shall be proven beyond reasonable doubt deal with the doubt, so their essence and use could probably throw some light on the above questions. Whilst in dubio pro reo principle is common for most of the continental law countries, the standard of beyond reasonable doubt developed in the Anglo-Saxon world, but it has been ‘recently’ introduced on the continent as well. Nowadays, the two can have very similar, if not identical, effect and probably could have had it at different stages in the past as well. It does not mean the origin and the circumstances in which the two emerged and developed were the same. Yet, most scholars would probably agree that today both of them reflect the realistic tendency of any conscientious person or a good society to protect themselves from injustice because the purpose of the overall criminal justice to punish the guilty at the same time has the other side, acquitting the innocent. By comparing the two one can notice that unlike the standard of proving the guilt beyond reasonable doubt by the prosecution, which is applied in the end of the trial once the court has heard and seen all the evidence and is to decide on the guilt (or innocence) of the defendant, the in dubio pro reo principle literally does not restrict the moment of its application. Therefore, some may argue that in dubio pro reo has wider application and can be used in all stages of the criminal procedure, such as the stage when the court decides on imposing detention or when it accepts or rejects the Indictment, etc. However, given the fact that a judge can be doubtful during the trial, moreover, even prior to the trial, a question arises whether a judge should always apply the principle of in dubio pro reo and decide in favour of the defendant by halting the criminal procedure? Certainly not. Instead, the judge shall decide whether the prosecution has met the other necessary standards for undertaking certain investigative measures, restrictions and charges, such as the standard of reasonable suspicion that the defendant has committed the crime. Moreover, the domestic LCP requires that the court applies the principle of in dubio pro reo only when decides whether facts exist or not, which the court decides