Criminal proceedings in Ukraine are based on the adversarial principle, as outlined in Part 1 of Article 22 of the Criminal Procedure Code of Ukraine. However, during the pre-trial investigation, the prosecution has significantly more powers and information than the defense, which raises questions about the scope of adversarial proceedings and equality of the parties at this stage of criminal proceedings.

The purpose of this study is to substantiate the non-absolute legal nature of the principles of adversarial proceedings and equality of the parties at the stage of pre-trial investigation, to determine the peculiarities of the implementation of adversarial proceedings and equality of the parties at the stage of pre-trial investigation, to clarify the expediency of applying the principles of adversarial proceedings and equality of the parties at the stage of pre-trial investigation, and formulating the concept of synergy between part two of Article 87 of the CPC of Ukraine and part three of Article 6 of the Convention for the Protection of Human Rights and Fundamental Freedoms as a criterion for determining the scope of application of the principles of adversarial proceedings and equality of the parties at the above-mentioned stage of criminal proceedings.

The authors concluded that the principles of adversarial proceedings and equality of the parties are not absolute at the pre-trial investigation stage; however, they play a fundamental role in guaranteeing human rights – including the right to defense, access to court, and others. The authors provide their vision of the synergy between part two of Article 87 of the CPC of Ukraine and part three of Article 6 of the Convention as the limits of application of the principles under study. The results of the study can be used as a basis for assessing the overall fairness of criminal proceedings or the admissibility of evidence collected and presented by the parties in criminal proceedings.

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