Through textual analysis of current legislation and theoretical approaches, the article aims to define the essence of human rights investigation in a criminal proceeding and outline challenging issues that arise during its implementation. It has been clarified that in the current stage of criminal procedural law development, it is entirely acceptable to consider defense counsel’s activity in a criminal proceeding as a form of human rights investigation. This involves the defense counsel utilizing powers granted by law to uncover the actual circumstances surrounding the commission of a criminal offense, document relevant factual data, and demonstrate their significance, admissibility, and persuasiveness to the prosecution, investigating judge, and court. The above varies based on the stage of a criminal proceeding and the nature of tasks at hand. It has been established that conducting such investigations within defense undertaken by designation is permissible, while the legalization of collected materials is possible only under certain criteria.