By becoming a party of the Convention for the Protection of Human Rights and Fundamental Freedoms, the Republic of Croatia took responsibility to respect conventional rights, one of which is the right to a fair trial guaranteed in Article 6. It represents one of the most important procedural rights on the basis of which subjective rights of each individual should be decided. In order to exercise this right, it is necessary that a person who believes that his rights and legal interests have been violated by a decision of a public authority made in an administrative procedure, has the opportunity to challenge such a decision. Therefore, at the very center of this paper is a presentation of the expert evidence in an administrative in order to decide on his rights by a legal decision, made on the basis of fully and properly established facts. The paper is divided into 7 chapters. After the introduction (chapter 1), the second chapter explains expert evidence as one of the types of evidence in an administrative dispute, its function and the rules on the burden of proof. The third chapter describes how the right to a fair trial is realized in an administrative dispute, and the fourth chapter gives a special overview of expert evidence as a guarantee for ensuring a fair trial. The fifth chapter deals with the question of how the right to a fair trial is violated in an administrative dispute, and the next chapter discusses certain aspects of the legal protection that an individual is entitled to in the event of a violation of his right to a fair trial, along with the relevant case law of the European Court of Human Rights. The paper ends with a conclusion on the importance of legal expert evidence before administrative courts, which contributes to strengthening the principles of the rule of law and the principles of a democratic society.