In this article, the author referred to the definition of the notion of an expert (court expert, ad hoc expert, ad casum expert) and its rights and obligations. She also indicated the form of appointing an expert, including a scientific institute (scientific and research institute), resulting from the provisions of law. In addition, she presented her views on the status of former court experts – i.e. people who once held this function – and also pointed out the differences between an expert and a witness.