The topic of this Master thesis is the role and importance of doctors and other medical professionals as expert witnesess in criminal proceedings, with reference to the influence of the independence and impartiality of such expertise on the course and outcome of criminal proceedings, which was particularly problematic in the judgment of the European Court of Human Rights Bajić v. Croatia. Provisions on expert witnesess can be found Chapter XVIII. of the Croatian Criminal Procedure Act, specifically in articles 308 to 328, and fall under evidentiary actions in criminal proceedings. An expert witness's testimony is considerd a crutial evidence in criminal proceedings from which the Court and other bodies of criminal proceedings concludes about the existence or non-existence of facts that can only be established with the help of professional knowledge and skills an expert witness posesses. Given that the findings and opinions of expert witnesses represent significant, and sometimes the only reliable means of evidence in criminal proceedings, this thesis primarily deals with the extremely important role of doctors as expert witnesess and highlights the question of their impartiality when it comes to proceedings regarding the commission of criminal offenses against People's Health. The first part of the thesis begins with a historical overview of the development of forensic medicine and the institute of expert witness and an overview of the provisions of the Croatian Criminal Procedure Act, Courts Act and the Ordinance on the Appointment of Permanent Expert Witnesess, which regulate the general position of expert witnesess in criminal proceedings in Croatia. Furthermore, the thesis analyzes the specific role of the doctor as an expert witness through the prism of legal provisions, with an emphasis on his expertise, and also with reference to the most well-known and common medical expertise in criminal proceedings, such as body examination and autopsy, physical injury expertise, molecular genetic analysis, and psychiatric expertise examination. The thesis ends with a brief summary of the judgment of the European Court of Human Rights in the case of Bajić v. Croatia, in which the applicant emphasized the independence of the expert witness, and the Court found a violation of Articles 2 and 13 of the Convention for the Protection of Human Rights and Fundamental Freedoms.