Ensuring equality between parties and adhering to the adversarial principle is crucial, necessitating the availability of all procedural mechanisms to observe the rights and legitimate interests of both the defense counsel and the prosecution. Given the declarative nature of specific provisions outlining the procedure for involving a forensic expert by a defense counsel during the pre-trial investigation stage, the Article Purpose is defined as clarifying the specifics of involving a forensic expert by a defense counsel to conduct a qualified forensic examination at the stage of pre-trial investigation, presenting problematic aspects of such activity. Based on the analysis of investigative and judicial practices, proven methods for involving a forensic expert by a defense counsel have been identified. Recommendations have been formulated on the procedure for appealing against decisions by investigators and prosecutors to refuse to grant a motion for a forensic examination.